Direct-current interconnected power distribution network optimal scheduling method based on converter control switching

Abstract

The invention belongs to the technical field of electric power engineering. The DC interconnected power distribution network optimal scheduling method based on converter control switching is used for solving the problems of power distribution network voltage out-of-limit, low scheduling efficiency and the like under the high permeability of new energy, VSC network following and VSC network construction dual-mode cooperative control is adopted, a photovoltaic-energy storage-VSC multi-level voltage stability support system is constructed, and the optimal scheduling of the DC interconnected power distribution network is realized. Dual-mode undisturbed switching is realized through virtual quantity calculation and proportion superposition; a cross-regional power mutual aid mechanism is established based on a direct current channel, and an electricity purchasing cooperative control system is established in combination with time-of-use electricity price. According to the method, collaborative optimization of voltage stabilization and economic dispatching is realized, the new energy consumption capability is improved, the power purchase cost of a superior power grid is reduced, and the method is suitable for a'source-grid-load-storage 'collaborative dispatching scene.

Description

Technical Field

[0001] This invention relates to the field of power engineering technology, and specifically to an optimized scheduling method for DC interconnected distribution networks based on converter control switching. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Currently, the large-scale integration of distributed photovoltaic (PV) and energy storage devices into distribution networks has resulted in a complex "source-grid-load-storage" multi-faceted collaborative structure. However, the volatility and randomness of new energy output can easily lead to problems such as voltage exceeding limits at distribution network nodes and reverse power flow. Traditional distribution networks relying on on-load tap changers or voltage regulators are no longer sufficient to meet voltage control requirements. With advancements in power electronics technology, AC / DC hybrid distribution technology, due to its advantages of large capacity, low loss, and ease of integration with new energy sources and loads, has been piloted in medium- and low-voltage distribution networks. Therefore, the development of AC / DC hybrid distribution systems and their key technologies is of paramount importance for enhancing the flexible control capabilities of distribution networks and promoting the construction of new power systems.

[0004] Voltage source converters (VSCs), as core equipment for AC / DC energy conversion, possess active and reactive power decoupling control capabilities. However, their single control mode struggles to simultaneously address the voltage stability and economic dispatch requirements of the distribution network. Current technologies primarily employ a grid-following control mode, passively following the grid voltage phase and unable to actively support the voltage of passive networks. Some studies introduce a grid-connected control mode to simulate synchronous generator characteristics, but lack dynamic switching mechanisms with the grid-following mode and multi-resource collaborative optimization strategies, making it difficult to cope with the multi-objective dispatch requirements under complex distribution network operation scenarios. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an optimized scheduling method for DC interconnected distribution networks based on converter control switching. It designs a dual-mode collaborative control strategy for VSC (Voltage Control System) to follow the grid / build the grid, and establishes a three-in-one optimization system of "topology-control-scheduling" to achieve coordinated optimization of distribution network voltage stability support and economic scheduling.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for optimizing the scheduling of DC interconnected distribution networks based on converter control switching.

[0007] A method for optimized scheduling of DC interconnected distribution networks based on converter control switching includes the following processes: Construct a multi-level voltage stability support system that coordinates photovoltaic, energy storage, and VSC. The photovoltaic power station dynamically adjusts its reactive power output based on the node voltage deviation, and the energy storage system provides adaptive reactive power compensation based on the voltage drop depth. Real-time acquisition of voltage and current data and actual line parameters at PCC points in the distribution network. When a node voltage exceeds the limit or power fluctuation exceeds the preset range, a virtual output voltage is generated for the network control based on the acquired data, so that the output reference value of the grid-following control loop and the network control loop are matched, realizing a smooth transition of VSC from grid-following mode to network mode. Active voltage or frequency support and inertia supplementation are provided through the virtual synchronous machine characteristics of the network mode. A cross-regional power mutual assistance mechanism is established based on DC interconnection channels. The surplus power in areas rich in new energy is transferred to the load center by utilizing the active power regulation capability of VSC. The day-ahead charging and discharging plan of the energy storage system is formulated by combining photovoltaic and load forecasts. In real-time operation, the photovoltaic output deviation is compensated by adjusting the active power transmission power of VSC. Establish a power purchase coordination control mechanism to deliver surplus power through VSC and coordinate energy storage charging during photovoltaic power generation periods. Prioritize energy storage discharge during peak load periods. When energy storage power reaches its upper limit, introduce surplus power through VSC to smooth out peak power purchases. When the system returns to normal voltage and power fluctuations meet normal thresholds, virtual output current is generated for GFL control based on actual line parameters and PCC point operating data, realizing a smooth transition of VSC from grid-connected mode to grid-following mode, and maintaining continuous optimized operation of the distribution network.

[0008] In one implementation of the first aspect of the present invention, the reactive power output adjustment of the photovoltaic system adopts a voltage prediction-real-time tracking dual-layer control mechanism. Voltage prediction generates a voltage reference value based on historical node voltage data and environmental factors. Real-time tracking dynamically allocates reactive power output based on the deviation between the actual node voltage and the voltage reference value to ensure the capacity required for maximum power point tracking.

[0009] In one implementation of the first aspect of the present invention, the adaptive compensation strategy of the energy storage system includes: presetting two voltage deviation thresholds; when the node voltage deviation does not exceed the first threshold, outputting reactive power according to the first response coefficient; when the voltage deviation is between the first threshold and the second threshold, outputting basic compensation power according to the second response coefficient; when the voltage deviation exceeds the second threshold, outputting the maximum reactive capacity; and during the transition phase of VSC1 or VSC2 mode switching, the energy storage system outputs reactive power to compensate for the reactive power output fluctuation of VSC, so as to avoid voltage regulation interruption.

[0010] In one implementation of the first aspect of the present invention, the cross-regional power mutual assistance mechanism includes: analyzing the spatiotemporal distribution differences between the photovoltaic system and the load at the node, breaking through the radial operation constraints of the traditional AC distribution network through the bidirectional power controllability characteristics of the VSC, and transferring the surplus power of the photovoltaic-rich area to the load center through the DC interconnection channel.

[0011] In one implementation of the first aspect of the present invention, the energy storage-VSC dual-layer optimization strategy includes: in the day-ahead phase, based on the next day's photovoltaic output forecast and load forecast, a charging and discharging plan for the nodal energy storage system is formulated with the goal of minimizing the electricity purchase cost; in the real-time phase, when the actual photovoltaic output deviates from the forecast value, the active power transmission power of the VSC is dynamically adjusted to offset the deviation and reduce unplanned charging and discharging of the energy storage system.

[0012] In one implementation of the first aspect of the present invention, a hybrid proportional control strategy is adopted for smooth transition. The network-following control loop and the network-building control loop always operate in closed loop at the same operating point through virtual quantity calculation and proportional superposition mechanism. The triggering condition for switching from network-following mode to network-building mode is that the node voltage is lower than 0.95 pu or the power fluctuation is greater than the preset fluctuation threshold. The triggering condition for switching from network-building mode to network-following mode is that the node voltage is between 0.98 pu and 1.02 pu and the power fluctuation is less than the preset fluctuation threshold.

[0013] In one implementation of the first aspect of the present invention, the network control is based on virtual inertia-excitation cooperative logic. The synchronous generator rotor motion and excitation regulation characteristics are modeled through a virtual synchronous generator algorithm. The virtual mechanical torque and electromagnetic torque deviation are input into the rotor motion equation to generate virtual angular velocity and power angle reference signals. The excitation regulation module dynamically corrects the AC side voltage reference value according to the power angle deviation. After processing by the voltage outer loop and the current inner loop, a modulation signal is generated to drive the converter.

[0014] Secondly, the present invention provides an optimized scheduling system for DC interconnected distribution networks based on converter control switching.

[0015] A DC interconnected distribution network optimization dispatching system based on converter control switching includes: The voltage stability support unit is configured to: construct a multi-level voltage stability support system that coordinates photovoltaic-energy storage-VSC; the photovoltaic power station dynamically adjusts reactive power output based on node voltage deviation; and the energy storage system provides adaptive reactive power compensation based on voltage drop depth. The mode switching trigger unit is configured to: collect voltage and current data and actual line parameters of the distribution network PCC point in real time; when the node voltage exceeds the limit or the power fluctuation exceeds the preset range, generate a virtual output voltage for the network control based on the collected data, so that the output reference value of the grid control loop matches the output reference value of the grid control loop, realize the smooth transition of VSC from grid mode to network mode, and provide active voltage or frequency support and inertia supplement through the virtual synchronous machine characteristics of the network mode; The power mutual assistance dispatch unit is configured to: establish a cross-regional power mutual assistance mechanism based on the DC interconnection channel; utilize the active power regulation capability of VSC to transfer the surplus power in the new energy rich area to the load center; formulate the day-ahead charging and discharging plan of the energy storage system in combination with photovoltaic and load forecasting; and compensate for photovoltaic output deviation by adjusting the active power transmission power of VSC in real time operation. The power purchase coordination peak shaving unit is configured to: construct a power purchase coordination control mechanism, transmit surplus power through VSC and coordinate energy storage charging during photovoltaic power generation periods, prioritize energy storage discharge during peak load periods, and introduce surplus power through VSC to smooth out peak power purchases when the energy storage power reaches its upper limit. The recovery mode switching unit is configured to generate a virtual output current for GFL control based on actual line parameters and PCC point operating data when the system recovers to normal voltage and power fluctuation meets normal threshold, so as to realize the smooth transition of VSC from grid-connected mode to grid-following mode and maintain the continuous optimized operation of the distribution network.

[0016] Thirdly, the present invention provides a computer device, comprising: a processor and a computer-readable storage medium; A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the DC interconnected distribution network optimization scheduling method based on converter control switching, which is the first aspect of the present invention.

[0017] Fourthly, the present invention provides a computer-readable storage medium storing a computer program adapted to be loaded by a processor and executed by the DC interconnected distribution network optimization scheduling method based on converter control switching according to the first aspect of the present invention.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention innovatively proposes a converter control switching scheme that optimizes economic dispatch while ensuring voltage support. By switching between different converter control modes, the system can better cope with sudden load changes and provide a stable power supply. Simulation verification shows that the proposed converter control switching scheme can reduce the upstream power purchase cost and form a power purchase optimization system that integrates new energy consumption, energy storage buffering, and VSC power regulation. This provides a collaborative optimization path for the safe and economical operation of distribution networks with high new energy penetration and offers a useful technical reference for the integrated development of "source, load, and storage" in new power systems.

[0019] This invention constructs a multi-level voltage stability support system, enabling photovoltaic and energy storage to participate in voltage regulation in tandem, thereby enhancing the distribution network's ability to cope with new energy fluctuations. Through smooth switching of VSC mode, it provides active voltage and frequency support during system anomalies, ensuring operational stability. A cross-regional power exchange mechanism enables efficient transfer of surplus new energy power, reducing curtailment. A power purchase coordination control mechanism, combining energy storage and VSC regulation, smooths out peak power purchases and reduces power purchase costs. After the system returns to normal, VSC can smoothly switch back to grid-connected mode, ensuring the distribution network remains in optimized operation for an extended period, achieving overall synergy between voltage stability and economic dispatch.

[0020] This invention uses a voltage prediction stage to determine a reasonable voltage benchmark by combining historical data and environmental factors, providing a precise basis for subsequent adjustments. The real-time tracking stage dynamically allocates reactive power output based on the deviation between the actual voltage and the benchmark value, which not only ensures the stability of the node voltage but also prioritizes the active power capacity required for photovoltaic maximum power point tracking, avoiding the impact of reactive power adjustment on photovoltaic power generation efficiency. This allows photovoltaics to fully realize its power generation potential while participating in voltage control, improving the economy and stability of new energy utilization.

[0021] This invention enables the energy storage system to flexibly adjust reactive power output according to the voltage drop depth by preset different voltage deviation thresholds. It can precisely adjust when the voltage fluctuates slightly and fully compensate when it fluctuates significantly, ensuring that the voltage quickly returns to stability. During the transition phase of VSC mode switching, the energy storage system can promptly compensate for the reactive power output fluctuations of VSC, effectively avoiding the problem of interruption in voltage regulation, preventing the voltage instability during the transition phase from affecting the power supply quality of the distribution network, and further strengthening the voltage support capability of the distribution network.

[0022] This invention deeply analyzes the spatiotemporal distribution differences between photovoltaics and loads, and utilizes the bidirectional power controllability of VSC to break the limitations of the radial operation of traditional AC distribution networks, thus constructing an efficient power transfer channel. It can directionally transmit the surplus power in photovoltaic-rich areas to load centers, effectively alleviating the curtailment pressure in renewable energy-rich areas, while meeting the electricity demand of load centers, achieving optimized allocation of power resources between regions, and improving the renewable energy absorption capacity and operating efficiency of the entire distribution network.

[0023] In the day-ahead phase of this invention, the goal is to minimize electricity purchase costs. It combines photovoltaic (PV) and load forecasting to formulate energy storage charging and discharging plans, providing scientific preliminary planning for system operation. In the real-time phase, when there is a deviation between PV output and forecast, the deviation is offset by adjusting the active power transmission of the VSC (Vehicle Storage System), reducing unplanned charging and discharging of energy storage, reducing energy storage cycle losses, extending energy storage lifespan, and ensuring system power balance. This avoids power supply instability caused by PV fluctuations, balancing system economy and operational stability.

[0024] This invention ensures that the grid-following control loop and the grid-building control loop always operate in closed loop at the same operating point through virtual quantity calculation and proportional superposition mechanism, eliminating transient impacts during mode switching and achieving a disturbance-free transition; the clear mode switching trigger conditions allow the VSC to switch to grid-building mode in a timely manner to provide support when the system voltage or power is abnormal, and smoothly switch back to grid-following mode after the system returns to normal, ensuring that the distribution network can operate stably under different operating conditions and improving the system's adaptability to complex operating scenarios.

[0025] This invention utilizes a virtual synchronous generator algorithm to accurately model the rotor motion and excitation regulation characteristics of a synchronous generator, enabling the VSC to possess inertia and voltage support capabilities similar to a synchronous generator. By transmitting torque deviation into the rotor motion equation to generate a key reference signal, and combining this with the excitation regulation module to dynamically correct the voltage reference value, the signal is processed through outer and inner loops to drive the converter. This allows the VSC to proactively provide stable voltage and frequency support in grid-connected mode, enhancing the distribution network's anti-disturbance capability. Especially in scenarios with high penetration of new energy sources, it effectively improves the dynamic stability of the system.

[0026] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 A flowchart illustrating an exemplary embodiment of the present invention provides a method for optimizing the scheduling of DC interconnected distribution networks based on converter control switching. Figure 2 An AC system topology is provided as an exemplary embodiment of the present invention; Figure 3 A schematic diagram of a network control strategy provided as an exemplary embodiment of the present invention; Figure 4 A schematic diagram of a network control strategy provided as an exemplary embodiment of the present invention; Figure 5 A power purchase price curve provided as an exemplary embodiment of the present invention; Figure 6 A node voltage curve provided as an exemplary embodiment of the present invention; Figure 7 A converter voltage curve provided as an exemplary embodiment of the present invention; Figure 8 A converter reactive power curve is provided as an exemplary embodiment of the present invention; Figure 9 An energy storage charge / discharge power curve provided as an exemplary embodiment of the present invention; Figure 10 A converter control mode switching curve provided as an exemplary embodiment of the present invention; Figure 11 A fixed control mode is provided as an exemplary embodiment of the present invention, showing the power purchase curve from the upper-level power grid; Figure 12 A power purchase curve from the upstream power grid is provided as an exemplary embodiment of the present invention; Figure 13 A schematic diagram of a DC interconnected distribution network optimization scheduling system based on converter control switching, provided as an exemplary embodiment of the present invention; Figure 14 A schematic diagram of a computer device provided for an exemplary embodiment of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0031] As mentioned in the background technology, the current operation of distribution networks with high renewable energy penetration faces three core dilemmas: First, in terms of voltage stability regulation, the fluctuation of renewable energy output and the randomness of load result in frequent voltage exceedances at nodes. Traditional voltage regulation methods that rely on energy storage charging and discharging are limited by energy storage capacity constraints and cannot achieve rapid voltage recovery. Second, in terms of converter control, existing VSCs mostly adopt a single grid-following control mode, passively following the grid voltage phase and unable to actively support the voltage amplitude and frequency of the distribution network. In contrast, the power transmission flexibility under the independent grid control mode is insufficient, and there is a lack of a smooth switching mechanism with the grid-following mode. Third, in terms of system coordinated scheduling, there is a lack of a unified optimization framework among distributed photovoltaic, energy storage and VSC. The photovoltaic curtailment rate is high, and the energy storage's frequent participation in voltage regulation leads to increased cycle losses, resulting in high electricity purchase costs from the upstream grid.

[0032] To address the aforementioned challenges, this implementation innovatively proposes a DC interconnected distribution network optimization scheduling method based on converter control switching. It designs a dual-mode collaborative control strategy for VSC (Vehicle Switching Control) with the grid / network construction, establishing a three-in-one optimization system of "topology-control-scheduling" to achieve coordinated optimization of distribution network voltage stability support and economic dispatch. Based on an AC distribution network scenario, a VSC control switching optimization scheduling scheme is proposed. The system consists of AC systems, photovoltaics, and energy storage components, with AC systems interconnected via VSCs for DC transmission. Figure 1 The structural topology of the communication system is shown. Specifically, the scheduling method includes the following processes: S101: Design of voltage stability support capability for distribution networks.

[0033] In this distribution network, a multi-level voltage stability control system is constructed with photovoltaic (PV) and energy storage as the main support and VSC (Voltage Control System) as the collaborative optimization core architecture. This system focuses on leveraging the active regulation capabilities of PV and energy storage to solidify the voltage support foundation, and improves the system's stable operation under extreme conditions through VSC grid-following / grid-connection mode switching. In the specific collaborative design of each component, the PV power plant, as an important carrier of distributed reactive power resources, must first ensure the active power capacity required for maximum power point tracking (MPPT). At this point, the maximum adjustable reactive power capacity of the PV inverter... The following capacity and power factor constraints must be met: (1); In the formula, The rated capacity of the inverter, To ensure timely and effective work, To achieve the minimum power factor, This is the reactive power adjustable coefficient.

[0034] Dynamic reactive power compensation based on nodal voltage deviation The following local control law is used to achieve a rapid response to voltage over-limits: (2); In the formula, For the real-time voltage of the node, As voltage boundary, To provide the target pressure margin, This refers to the line reactance.

[0035] Leveraging its millisecond-level response characteristics, the energy storage system serves as the core execution unit for voltage support, employing an adaptive compensation strategy based on voltage sag depth. When a node voltage deviation exceeds a preset threshold, the energy storage system immediately outputs reactive power compensation, effectively smoothing out voltage transient fluctuations. To achieve seamless coverage and coordination within the energy storage system, an adaptive variable step-size function is introduced. To balance response speed and steady-state error: (3); In the formula, This refers to the consistency deviation of voltage or state of charge. Let be the adjustment step size for the k-th iteration, and a, b, c, and d be shape parameters. This mechanism ensures that the energy storage system can quickly adjust its output based on the drop depth when it detects a deviation exceeding a threshold.

[0036] In this architecture, VSC undertakes system-level optimization and extreme support functions. VSC1 is in grid-following mode during normal operation. Through active-reactive decoupling control, it coordinates with the regulation behavior of the photovoltaic and energy storage system to optimize power flow distribution and reduce the regulation pressure on photovoltaic and energy storage equipment. VSC2 is in grid-connection control mode. Relying on virtual synchronous machine technology, it provides active voltage support and inertial response, enhances the stability boundary of the system, and avoids voltage over-limit problems when photovoltaic power drops sharply, energy storage reaches its capacity limit, or encounters short-circuit faults.

[0037] S102: Design of distribution network optimization dispatch capability.

[0038] This distribution network employs an optimized dispatching system with multi-entity collaborative power transmission as its core architecture. It leverages DC interconnection channels to construct a cross-regional power mutual assistance mechanism, comprehensively enhancing the system's operational flexibility and economy. An optimization function is established with the objective of minimizing the cost of purchasing electricity from the upper-level grid throughout the entire power cycle, as specifically expressed below: (4) in, The scheduling period is 24 hours. Let t be the time-of-use electricity price. Let t be the active power purchased by the distribution network from the upstream power grid.

[0039] At the power transmission level, a distributed optimization model for dynamic cross-regional power allocation is established based on DC interconnection channels. The AC and DC regions are interconnected via VSCs, with the goal of minimizing overall system operating costs. By analyzing the spatiotemporal distribution differences of distributed power sources and loads, and utilizing the rapid active power regulation capabilities of VSCs, surplus power in renewable energy-rich areas is directionally transferred to load centers. This achieves optimized cross-regional allocation and efficient local consumption of renewable energy, effectively alleviating the problem of curtailment caused by resource constraints in local areas. The following optimization objectives are established, and power transfer is achieved by adjusting the exchange power with the AC region: (5); In the formula, and These represent the power flowing from the VSC to the AC region and the power absorbed from the AC region (i.e., the amount of surplus power transferred). This refers to the internal settlement price or shadow price between regions.

[0040] At the level of coordinated operation between energy storage and VSC, the charging and discharging plan of the energy storage system is formulated based on new energy and load forecasts during the day-ahead phase. During real-time operation, when the actual output of photovoltaic power deviates from the forecast curve, the active power transmission power of the VSC is dynamically adjusted to compensate for the power deviation, reducing the unplanned charging and discharging voltage of the energy storage, thereby extending its operational life and improving its overall economic efficiency. To achieve power mutual assistance and deviation compensation by the VSC, its operation must meet capacity constraints and loss characteristics. (6); (7); With the aim of reducing the cost of electricity purchase from the upper-level power grid, a collaborative control mechanism for electricity purchase will be further constructed. During the photovoltaic power generation period, surplus power will be directed to high-load areas using VSC (Vehicle Storage System), enhancing the local consumption capacity of new energy and reducing the demand for electricity purchase from the upper-level grid due to power shortages. At the same time, the collaborative energy storage system will charge and store energy during periods of abundant photovoltaic power generation, realizing energy time-shifting and providing localized power supply support for subsequent peak load periods, effectively replacing high-priced grid-connected electricity.

[0041] To address the peak electricity purchase issue caused by load fluctuations, a joint peak-shaving strategy is designed, combining priority discharge of energy storage with complementary power from VSC (Vehicle Storage System). This strategy satisfies the following equation: (8); (9) (10); in, For energy storage, For charging and discharging power, For efficiency, It is a 0-1 state variable to ensure that the energy storage will not be charged and discharged at the same time.

[0042] Before peak load arrives, the energy storage system is charged to the target state of charge based on forecast information. During peak periods, the energy storage system discharges as the primary regulation resource. When its power output reaches its upper limit, the active power transmission direction and amplitude of the VSC (Vehicle Grid Storage System) are adjusted to introduce surplus power from the other distribution network or real-time photovoltaic output, thus coordinating to smooth out peak electricity purchases. Based on the actual fluctuations in photovoltaic power and load, the VSC power command and energy storage actions are dynamically corrected to avoid increased electricity purchase costs due to forecast deviations. Ultimately, this forms a three-in-one electricity purchase optimization system integrating efficient new energy consumption, dynamic energy storage buffering, and cross-regional VSC regulation.

[0043] S103: Interconnect converter control strategy.

[0044] As a key component in AC and DC systems, the proper control of the interconnect converter is crucial for maintaining system stability. This paper describes a VSC converter employing a "dual-mode collaborative + adaptive switching" control architecture, achieving precise matching of power regulation and voltage support through hierarchical control. The following sections will introduce grid-connected control, grid-connected control, and the corresponding switching methods.

[0045] The grid-following control is based on the "voltage tracking-power decoupling" control logic. Specifically, it is implemented as follows: A phase-locked loop (PLL) acquires the voltage phase and amplitude at the AC side's point of common coupling (PCC) in real time, using this as a reference signal. This signal is then fed into the inner current loop and outer power loop controllers in the dq coordinate system. The outer power loop calculates the current reference value based on the active and reactive power commands issued by the central controller, tracks this current reference value in the inner current loop, and generates a modulation signal. This signal is then used to drive the converter switching devices via a pulse width modulation (PWM) module. The specific control strategy is as follows: Figure 3 As shown, the model formula for this control strategy is as follows: Phase-locked loop control equations: (11); (12); In the formula, For the voltage at point PCC q Axial components, This is the fundamental angular frequency of the power grid.

[0046] Power outer loop control: (13); (14); In the formula, the given active power reference value and reactive power reference value Inner loop current reference value , .

[0047] Inner current control: (15); (16); In the formula, This is a filter inductor.

[0048] The network control is based on the "virtual inertia-excitation coordination" control logic. Specifically, it is implemented as follows: The rotor motion and excitation regulation characteristics of the synchronous generator are modeled using a Virtual Synchronous Generator (VSG) algorithm. The deviation between virtual mechanical torque and electromagnetic torque is input into the rotor motion equation, generating virtual angular velocity and power angle reference signals. The excitation regulation module dynamically corrects the AC side voltage reference value based on the power angle deviation, forming a voltage-frequency support command. This command is processed by the voltage outer loop and current inner loop controllers in the dq coordinate system to generate a modulation signal, which drives the converter switching devices via the PWM module, achieving active voltage and frequency support. The specific control strategy is as follows: Figure 4 As shown. The model formula for this control strategy is as follows: Virtual rotor motion equations (active power-frequency loop): (17); In the formula, virtual inertia and damping , To output electromagnetic power, This is the virtual angular velocity.

[0049] Virtual excitation regulation equation (reactive power-voltage loop): (18); The formula for the inner current loop is the same as that for grid control; only the formula for the outer voltage loop control is shown here. (19); (20); This patent employs a hybrid proportional control strategy to achieve seamless switching between Grid Following (GFL) and Grid Forming (GFM) modes. The core idea is to use virtual quantity calculation and proportional superposition mechanisms to ensure that the two control loops always operate in closed loop at the same operating point, eliminating switching fluctuations at the source. The specific process is as follows: Under normal and stable operating conditions, the GFL control mode is used to optimize cross-regional power transmission through power decoupling control, and to achieve efficient consumption and economical dispatch of new energy sources in conjunction with photovoltaic-energy storage. When disturbances or other problems occur, a virtual output voltage is generated for GFM control based on actual line parameters and the voltage and current at the PCC point, ensuring that the output reference values ​​of the two control loops are consistent with the actual system state, thus achieving a smooth transition from GFL to GFM. A virtual internal potential calculation model for the grid-connected mode is constructed as follows: (twenty one); Once transitioning to GFM control, the virtual synchronous generator characteristics can provide active voltage or frequency support and inertia replenishment, resolving the insufficient support capacity issue caused by output constraints in photovoltaic-energy storage. When the system recovers to normal voltage and power fluctuations meet normal thresholds, a virtual output current is generated for the GFL again based on line parameters, gradually switching to GFL control mode. A virtual current reference value calculation model for grid-connected mode is constructed: (twenty two); To verify the feasibility of the proposed optimized scheduling scheme, this paper transforms the Mixed Integer Nonlinear Programming (MINLP) model into a Mixed Integer Linear Programming (MILP) model using linearization techniques. Figure 2 The IEEE 33-node system topology shown was used to build a system model on the MATLAB simulation platform. Nodes 12 and 33 are connected to the photovoltaic system, nodes 17 and 25 are connected to the energy storage system, and nodes 8 and 22 are connected to VSC1 and VSC2 respectively. Under normal operation, VSC1 is in GFM control mode to maintain the system voltage, and VSC2 is in GFL control mode to control the power transmission.

[0050] The simulation experiment predicts 24-hour electricity price changes and reduces the purchase price from the upper-level grid by controlling the switching of the converter and coordinating the use of photovoltaic and energy storage components, thereby achieving economically optimized dispatch of the distribution network. The 24-hour electricity purchase price is as follows: Figure 4 As shown.

[0051] The safe and stable operation of the power distribution system is a crucial prerequisite for carrying out its optimized scheduling and other subsequent control tasks. To verify the system's operational safety, Figure 5 , 6 Section 7 shows the dynamic variation curves of node voltage, converter voltage, and reactive power of the power distribution system. The data characteristics in the figure show that throughout the entire analysis period, the highest and lowest voltages at any given time at each node remained within the rated voltage allowable range of 0.95~1.05 pu. Simultaneously, the system's reactive power remained in a balanced and stable state, without any voltage exceeding limits or reactive power imbalance affecting operational safety, thus fully ensuring the continuous and safe operation of the power distribution network.

[0052] Figure 8 , 9The dynamic characteristics of the charging and discharging power of the energy storage element and the switching process of the converter's control mode are presented to reveal the system's operation and regulation mechanism during different electricity price periods. During periods of low electricity prices, the energy storage element operates in a charging state, achieving efficient energy storage during low-price periods. Simultaneously, VSC2 switches from GFM control mode to GFL control mode, further reducing the control target of lowering the electricity purchase volume of the upstream grid by improving the active power transmission capacity. During periods of high electricity prices, the energy storage element switches to a continuous discharging state to release the stored energy, while VSC2 continuously maintains GFL control mode operation, effectively sharing the power transmission pressure of the upstream grid and avoiding its power supply overload.

[0053] Figure 10 , 11 The two graphs respectively present the power purchase variation curves from the upstream power grid. A comparison of the data characteristics shows that during periods of higher electricity prices, the power supplied by the power purchase curve through converter control mode switching is significantly less than that of the power supply curve in fixed control mode. This ultimately achieves the core objective of economically optimizing the operation of the distribution network, verifying the economy and effectiveness of the proposed control strategy.

[0054] Figure 13 An optimized dispatching system for DC interconnected distribution networks based on converter control switching is shown, comprising: The voltage stability support unit 1301 is configured to: construct a multi-level voltage stability support system that coordinates photovoltaic-energy storage-VSC; the photovoltaic power station dynamically adjusts reactive power output based on node voltage deviation; and the energy storage system provides adaptive reactive power compensation based on voltage drop depth. The mode switching trigger unit 1302 is configured to: collect voltage and current data and actual line parameters of the PCC point of the distribution network in real time; when the node voltage exceeds the limit or the power fluctuation exceeds the preset range, generate a virtual output voltage for the network control based on the collected data, so that the output reference value of the grid control loop and the network control loop are matched, realize the smooth transition of VSC from grid mode to network mode, and provide active voltage or frequency support and inertia supplement through the virtual synchronous machine characteristics of the network mode; The power mutual assistance dispatch unit 1303 is configured to: establish a cross-regional power mutual assistance mechanism based on the DC interconnection channel; utilize the active power regulation capability of VSC to transfer the surplus power in the new energy rich area to the load center; formulate the day-ahead charging and discharging plan of the energy storage system in combination with photovoltaic and load forecasting; and compensate for photovoltaic output deviation by adjusting the active power transmission power of VSC in real-time operation. The power purchase coordination peak shaving unit 1304 is configured to: construct a power purchase coordination control mechanism, transmit surplus power through VSC and coordinate energy storage charging during photovoltaic power generation periods, prioritize energy storage discharge during peak load periods, and introduce surplus power through VSC to smooth out peak power purchases when energy storage power reaches its upper limit. The recovery mode switching unit 1305 is configured to generate a virtual output current for GFL control based on actual line parameters and PCC point operating data when the system recovers to normal voltage and power fluctuation meets normal threshold, so as to realize the smooth transition of VSC from grid-connected mode to grid-following mode and maintain the continuous optimized operation of the distribution network.

[0055] It is understood that the aforementioned units can be individually or entirely merged into one or more other units, or some of the units can be further divided into multiple functionally smaller units. This achieves the same operation without affecting the technical effects of the embodiments of the present invention. The aforementioned units are based on logical functional division. In practical applications, the function of one unit can be implemented by multiple units, or the function of multiple units can be implemented by one unit. In other embodiments of the present invention, the system may also include other units. In practical applications, these functions can also be implemented with the assistance of other units, and can be implemented collaboratively by multiple units.

[0056] According to another embodiment of the present invention, the system of this embodiment can be constructed by running a computer program (including program code) capable of performing the steps involved in the corresponding method of the present invention on a general-purpose computing device, such as a computer, which includes processing elements and storage elements such as a central processing unit (CPU), random access memory (RAM), and read-only memory (ROM). The computer program can be recorded on, for example, a computer-readable recording medium, loaded into the aforementioned computing device through the computer-readable recording medium, and run therein.

[0057] Figure 14 A computer device is shown, which includes a processor 1401, a communication interface 1402, and a computer-readable storage medium 1403. The processor 1401, communication interface 1402, and computer-readable storage medium 1403 can be connected via a bus or other means.

[0058] The communication interface 1402 is used to receive and send data. The computer-readable storage medium 1403 can be stored in the memory of the electronic device. The computer-readable storage medium 1403 is used to store computer programs, which include program instructions. The processor 1401 is used to execute the program instructions stored in the computer-readable storage medium 1403.

[0059] The processor 1401 is the computing and control core of the electronic device. It is suitable for implementing one or more instructions, specifically for loading and executing one or more instructions to achieve the corresponding method flow or corresponding function.

[0060] Processor 1401 is configured to perform the following procedure: Construct a multi-level voltage stability support system that coordinates photovoltaic, energy storage, and VSC. The photovoltaic power station dynamically adjusts its reactive power output based on the node voltage deviation, and the energy storage system provides adaptive reactive power compensation based on the voltage drop depth. Real-time acquisition of voltage and current data and actual line parameters at PCC points in the distribution network. When a node voltage exceeds the limit or power fluctuation exceeds the preset range, a virtual output voltage is generated for the network control based on the acquired data, so that the output reference value of the grid-following control loop and the network control loop are matched, realizing a smooth transition of VSC from grid-following mode to network mode. Active voltage or frequency support and inertia supplementation are provided through the virtual synchronous machine characteristics of the network mode. A cross-regional power mutual assistance mechanism is established based on DC interconnection channels. The surplus power in areas rich in new energy is transferred to the load center by utilizing the active power regulation capability of VSC. The day-ahead charging and discharging plan of the energy storage system is formulated by combining photovoltaic and load forecasts. In real-time operation, the photovoltaic output deviation is compensated by adjusting the active power transmission power of VSC. Establish a power purchase coordination control mechanism to deliver surplus power through VSC and coordinate energy storage charging during photovoltaic power generation periods. Prioritize energy storage discharge during peak load periods. When energy storage power reaches its upper limit, introduce surplus power through VSC to smooth out peak power purchases. When the system returns to normal voltage and power fluctuations meet normal thresholds, virtual output current is generated for GFL control based on actual line parameters and PCC point operating data, realizing a smooth transition of VSC from grid-connected mode to grid-following mode, and maintaining continuous optimized operation of the distribution network.

[0061] This invention also provides a computer-readable storage medium, which is a memory device in an electronic device for storing programs and data. It is understood that the computer-readable storage medium here may include both built-in storage media in the electronic device and extended storage media supported by the electronic device. The computer-readable storage medium provides storage space for storing the processing system of the electronic device.

[0062] Furthermore, this storage space also contains one or more instructions suitable for loading and execution by the processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory; alternatively, it can also be at least one computer-readable storage medium located remotely from the aforementioned processor.

[0063] In one embodiment, the computer-readable storage medium stores one or more instructions; the processor loads and executes the one or more instructions stored in the computer-readable storage medium to perform the following process: Construct a multi-level voltage stability support system that coordinates photovoltaic, energy storage, and VSC. The photovoltaic power station dynamically adjusts its reactive power output based on the node voltage deviation, and the energy storage system provides adaptive reactive power compensation based on the voltage drop depth. Real-time acquisition of voltage and current data and actual line parameters at PCC points in the distribution network. When a node voltage exceeds the limit or power fluctuation exceeds the preset range, a virtual output voltage is generated for the network control based on the acquired data, so that the output reference value of the grid-following control loop and the network control loop are matched, realizing a smooth transition of VSC from grid-following mode to network mode. Active voltage or frequency support and inertia supplementation are provided through the virtual synchronous machine characteristics of the network mode. A cross-regional power mutual assistance mechanism is established based on DC interconnection channels. The surplus power in areas rich in new energy is transferred to the load center by utilizing the active power regulation capability of VSC. The day-ahead charging and discharging plan of the energy storage system is formulated by combining photovoltaic and load forecasts. In real-time operation, the photovoltaic output deviation is compensated by adjusting the active power transmission power of VSC. Establish a power purchase coordination control mechanism to deliver surplus power through VSC and coordinate energy storage charging during photovoltaic power generation periods. Prioritize energy storage discharge during peak load periods. When energy storage power reaches its upper limit, introduce surplus power through VSC to smooth out peak power purchases. When the system returns to normal voltage and power fluctuations meet normal thresholds, virtual output current is generated for GFL control based on actual line parameters and PCC point operating data, realizing a smooth transition of VSC from grid-connected mode to grid-following mode, and maintaining continuous optimized operation of the distribution network.

[0064] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can implement the described functions using different methods for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0065] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of the present invention is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in or transmitted through a computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic cable, digital cable) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that a computer can access or a data processing device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive), etc.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for optimized scheduling of DC interconnected distribution networks based on converter control switching, characterized in that, The process includes the following: Construct a multi-level voltage stability support system that coordinates photovoltaic, energy storage, and VSC. The photovoltaic power station dynamically adjusts its reactive power output based on the node voltage deviation, and the energy storage system provides adaptive reactive power compensation based on the voltage drop depth. Real-time acquisition of voltage and current data and actual line parameters at PCC points in the distribution network. When a node voltage exceeds the limit or power fluctuation exceeds the preset range, a virtual output voltage is generated for the network control based on the acquired data, so that the output reference value of the grid-following control loop and the network control loop are matched, realizing a smooth transition of VSC from grid-following mode to network mode. Active voltage or frequency support and inertia supplementation are provided through the virtual synchronous machine characteristics of the network mode. A cross-regional power mutual assistance mechanism is established based on DC interconnection channels. The surplus power in areas rich in new energy is transferred to the load center by utilizing the active power regulation capability of VSC. The day-ahead charging and discharging plan of the energy storage system is formulated by combining photovoltaic and load forecasts. In real-time operation, the photovoltaic output deviation is compensated by adjusting the active power transmission power of VSC. Establish a power purchase coordination control mechanism to deliver surplus power through VSC and coordinate energy storage charging during photovoltaic power generation periods. Prioritize energy storage discharge during peak load periods. When energy storage power reaches its upper limit, introduce surplus power through VSC to smooth out peak power purchases. When the system returns to normal voltage and power fluctuations meet normal thresholds, virtual output current is generated for GFL control based on actual line parameters and PCC point operating data, realizing a smooth transition of VSC from grid-connected mode to grid-following mode, and maintaining continuous optimized operation of the distribution network.

2. The DC interconnected distribution network optimization scheduling method based on converter control switching as described in claim 1, characterized in that, The reactive power output adjustment of the photovoltaic system adopts a voltage prediction-real-time tracking dual-layer control mechanism. The voltage prediction generates a voltage reference value based on historical node voltage data and environmental factors. The real-time tracking dynamically allocates reactive power output based on the deviation between the actual node voltage and the voltage reference value to ensure the capacity required for maximum power point tracking.

3. The DC interconnected distribution network optimization scheduling method based on converter control switching as described in claim 1, characterized in that, The adaptive compensation strategy of the energy storage system includes: preset two voltage deviation thresholds; when the node voltage deviation does not exceed the first threshold, reactive power is output according to the first response coefficient; when the voltage deviation is between the first threshold and the second threshold, the basic compensation power is output according to the second response coefficient; when the voltage deviation exceeds the second threshold, the maximum reactive capacity is output. During the mode switching transition phase, the energy storage system outputs reactive power to compensate for the reactive power output fluctuation of the VSC, so as to avoid voltage regulation interruption.

4. The DC interconnected distribution network optimization scheduling method based on converter control switching as described in claim 1, characterized in that, The cross-regional power sharing mechanism includes: analyzing the spatiotemporal distribution differences between the photovoltaic system and the load at the nodes, breaking through the radial operation constraints of the traditional AC distribution network through the bidirectional power controllability characteristics of the VSC, and transferring the surplus power of the photovoltaic-rich area to the load center through the DC interconnection channel.

5. The DC interconnected distribution network optimization scheduling method based on converter control switching as described in claim 1, characterized in that, The energy storage-VSC dual-layer optimization strategy includes: in the day-ahead phase, based on the next day's photovoltaic output forecast and load forecast, a charging and discharging plan for the nodal energy storage system is formulated with the goal of minimizing the electricity purchase cost; in the real-time phase, when the actual photovoltaic output deviates from the forecast value, the active power transmission of the VSC is dynamically adjusted to offset the deviation and reduce unplanned charging and discharging of the energy storage system.

6. The DC interconnected distribution network optimization scheduling method based on converter control switching as described in claim 1, characterized in that, The smooth transition adopts a hybrid proportional control strategy, which uses virtual quantity calculation and proportional superposition mechanism to ensure that the grid-following control loop and the grid-building control loop always operate in closed loop at the same operating point. The trigger condition for switching from grid-following mode to grid-building mode is that the node voltage is lower than 0.95 pu or the power fluctuation is greater than the preset fluctuation threshold. The trigger condition for switching from grid-building mode to grid-following mode is that the node voltage is between 0.98 pu and 1.02 pu and the power fluctuation is less than the preset fluctuation threshold.

7. The DC interconnected distribution network optimization scheduling method based on converter control switching as described in claim 1, characterized in that, The network control is based on virtual inertia-excitation cooperative logic. It models the rotor motion and excitation regulation characteristics of the synchronous generator through a virtual synchronous generator algorithm. The virtual mechanical torque and electromagnetic torque deviation are input into the rotor motion equation to generate virtual angular velocity and power angle reference signals. The excitation regulation module dynamically corrects the AC side voltage reference value according to the power angle deviation. After processing by the voltage outer loop and the current inner loop, a modulation signal is generated to drive the converter.

8. A DC interconnected distribution network optimized dispatching system based on converter control switching, characterized in that, include: The voltage stability support unit is configured to: construct a multi-level voltage stability support system that coordinates photovoltaic-energy storage-VSC; the photovoltaic power station dynamically adjusts reactive power output based on node voltage deviation; and the energy storage system provides adaptive reactive power compensation based on voltage drop depth. The mode switching trigger unit is configured to: collect voltage and current data and actual line parameters of the distribution network PCC point in real time; when the node voltage exceeds the limit or the power fluctuation exceeds the preset range, generate a virtual output voltage for the network control based on the collected data, so that the output reference value of the grid control loop matches the output reference value of the grid control loop, realize the smooth transition of VSC from grid mode to network mode, and provide active voltage or frequency support and inertia supplement through the virtual synchronous machine characteristics of the network mode; The power mutual assistance dispatch unit is configured to: establish a cross-regional power mutual assistance mechanism based on the DC interconnection channel; utilize the active power regulation capability of VSC to transfer the surplus power in the new energy rich area to the load center; formulate the day-ahead charging and discharging plan of the energy storage system in combination with photovoltaic and load forecasting; and compensate for photovoltaic output deviation by adjusting the active power transmission power of VSC in real time operation. The power purchase coordination peak shaving unit is configured to: construct a power purchase coordination control mechanism, transmit surplus power through VSC and coordinate energy storage charging during photovoltaic power generation periods, prioritize energy storage discharge during peak load periods, and introduce surplus power through VSC to smooth out peak power purchases when the energy storage power reaches its upper limit. The recovery mode switching unit is configured to generate a virtual output current for GFL control based on actual line parameters and PCC point operating data when the system recovers to normal voltage and power fluctuation meets normal threshold, so as to realize the smooth transition of VSC from grid-connected mode to grid-following mode and maintain the continuous optimized operation of the distribution network.

9. A computer device, characterized in that, include: Processor and computer-readable storage media; A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements the DC interconnected distribution network optimization scheduling method based on converter control switching as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program adapted to be loaded by a processor and executed as described in any one of claims 1 to 7 for the optimized scheduling method of DC interconnected distribution networks based on converter control switching.

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