Optimization method for asymmetric flexible interconnection alternating current and direct current hybrid power distribution network

Abstract

Belongs to the technical field of power system control, and aims to solve the problem that the power distribution network cannot be kept in an optimal working state due to the lack of a special optimization control method for the asymmetric flexible interconnection AC / DC hybrid power distribution network in the prior art. Establishing a topological model of the monitored object based on the topological structure of the flexible interconnection device, determining an optimization target and setting constraint conditions; and establishing an optimization model, and selecting a control strategy for implementing optimization according to the optimization model. Through an advanced power electronic conversion device and a control strategy, accurate control and optimization of the asymmetric flexible interconnection alternating current and direct current hybrid power distribution network on the power flow of the power grid are realized, so that the operation mode of an interconnection system is flexibly adjusted, and the continuity and stability of power supply are ensured; the transmission loss of the power distribution network can be reduced and the system energy efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power control systems, and particularly relates to an optimization method for an asymmetric flexible interconnected AC / DC hybrid distribution network. Background Art

[0002] A flexible interconnected AC / DC hybrid distribution network refers to a hybrid distribution network system that uses power electronic conversion devices (such as voltage source converters VSC, etc.) to connect an AC distribution network and a DC distribution network, forming a network that can transmit both AC and DC power. This system has a high degree of flexibility and can flexibly adjust the operation mode and power flow distribution of the distribution network according to different load demands and energy supply situations, achieving optimal allocation and efficient utilization of energy; through advanced power electronic conversion devices and control strategies, it can reduce the transmission loss of the distribution network and improve system energy efficiency. At the same time, the system also has high reliability, with self-recovery ability and fast response ability, and can quickly adjust the operation mode of the interconnected system when a fault occurs in the distribution network to ensure the continuity and stability of power supply. In addition, it uses advanced communication technology and control technology to achieve real-time monitoring, intelligent scheduling, and automatic optimization of the power grid, improving the operation efficiency and safety of the power grid. Moreover, the flexible interconnected AC / DC hybrid distribution network has a high degree of scalability and can be flexibly expanded and upgraded according to the needs of different regions, facilitating maintenance and management. With the rapid development of new energy and the accelerated construction of electric vehicle charging and swapping facilities, this system will become an important direction for the development of future medium and low voltage distribution networks. At the same time, with the continuous progress of technology and the rapid reduction of costs, its application scope will continue to expand.

[0003] Remarkable progress has been made in the research of DC distribution networks both at home and abroad, including the DC distribution system structure proposed in Europe in the early stage, soft-switching technology, energy routers, flexible DC connectors, and the application of modular multilevel AC-DC converters topology. These researches provide important support for building a more flexible, efficient, and reliable distribution network. In China, there is also a patent for invention, "A Flexible Interconnection Topology and Control Method for a Multi-port AC-DC Hybrid Distribution Network" with the application number CN202211606355.6. This patent also discloses a flexible interconnection topology structure and control method for a multi-port AC-DC hybrid distribution network. The flexible interconnection topology structure of the multi-port AC-DC hybrid distribution network consists of a DC-side AC / DC converter, a three-phase multiplexing circuit, and a three-phase AC-side multi-port feeder branch. The three-phase AC-side multi-port feeder branch includes n AC feeders, and each AC feeder includes an AC-side filter inductor and a voltage regulation circuit. The n AC feeders converge to a common AC bus and are connected to the corresponding phase multiplexing circuit, and the multiplexing circuit is connected to the DC-side AC / DC converter. By adjusting the voltage of the voltage regulation circuit on each port feeder, this invention changes the amplitude and phase of the AC-side voltage, realizing flexible interaction of active / reactive power and power flow control between multiple feeders. At the same time, the voltage regulation circuit of the AC feeder enables this topology to have the ability to ride through AC-side ground faults.

[0004] However, in the existing technology, the optimization methods for flexible interconnected AC-DC hybrid distribution networks are all based on the premise that the voltages on both sides of the distribution network are equal. In some special application scenarios, there is an interconnected mode where the voltages on both sides of the distribution network are asymmetric, and their operating voltages on both sides are not equal. Therefore, compared with the conventional flexible interconnection scheme of the distribution network, there are significant differences in its control strategy and protection logic, and the existing technology cannot be used for optimization. Summary of the Invention

[0005] The purpose of the present invention is to address the problem in the existing technology that there is a lack of a dedicated optimization method for asymmetric flexible interconnected AC-DC hybrid distribution networks, resulting in the distribution network being unable to maintain the best working state.

[0006] To this end, the present invention includes an optimization method for an asymmetric flexible interconnected AC-DC hybrid distribution network. For the target distribution network object, the target distribution network object is monitored. First, it is judged whether the voltages on both sides are symmetric. When it is confirmed that the voltages on both sides are asymmetric and no abnormality has occurred, a topological model of the monitoring object is established based on the topological structure of the flexible interconnection device, the optimization target is determined, and the constraint conditions are set. An optimization model is established, and a control strategy for implementing the optimization is selected according to the optimization model.

[0007] Preferably, the flexible devices installed in the topological model include a flexible loop closing device installed at the head end of the feeder. Equivalent to adding an additional auxiliary voltage source, a circulating current can be generated, making the distribution of current in the loop network more reasonable and also making the distribution of power flow in the loop network more reasonable. And a medium-voltage flexible interconnection system formed by connecting two voltage source converters in a back-to-back manner to an AC distribution line. The medium-voltage flexible interconnection system realizes functions such as electromagnetic loop network disconnection and fault isolation through independent control of active and reactive power in the AC system.

[0008] Preferably, the optimization objectives include balancing the line load rate and minimizing the active power loss of the line, and coordinating these two different optimization objectives.

[0009] Preferably, the control strategies for implementing the optimization include a line loop closing function without current impact, a power flow transfer function, a load transfer function, a fast disconnection function, and a fault ride-through function.

[0010] Preferably, the specific implementation steps of the line loop closing function are as follows: Collect the voltages at both ends of the flexible interconnection system acquisition device, and combine with the soft loop closing control algorithm to calculate the voltage amplitude and angle that the interconnection equipment needs to compensate. After the voltage output by the interconnection device is superimposed on the original voltage, it is closest to the voltage on the other side, achieving the optimization goal of minimizing the impact current during loop closing.

[0011] Preferably, the specific implementation steps of the power flow transfer function are as follows: For the normal operation condition of the distribution network, receive relevant control instructions issued by the monitoring system or the distribution dispatching main station, and adjust the flow direction and magnitude of active / reactive power flow between flexible interconnection feeders to achieve the optimization goal of mutual assistance of power flow and reasonable distribution of power between different feeders. At the same time, it also has the effects of reducing network loss and improving economic benefits.

[0012] Preferably, the specific implementation steps of the load transfer function are as follows: When a bus fault or planned maintenance condition is detected on one side of the distribution network, when the flexible interconnection device receives the load transfer instruction from the distribution dispatching main station, compare the transfer power with the power flow transfer capacity of the device. When the transfer power does not exceed the power flow transfer capacity of the device, it supports both load transfer through the flexible interconnection device and load transfer through the bypass switch; when the transfer power exceeds the transfer capacity of the device, it only supports load transfer through the bypass switch, so as to maintain the power supply to the non-faulty load on the faulty side. This can achieve uninterrupted power supply under the condition of a bus fault or planned maintenance on one side of the distribution network and improve the reliability of the distribution network.

[0013] Preferably, the specific implementation steps of the fast disconnection function are as follows: when a short-circuit fault occurs, the flexible interconnection device can disconnect the interconnection within the first reference time (usually 10 ms) and restore to the radial open-loop operation state. At the same time, when a short-circuit fault occurs, the distribution automation delays for the second reference time (usually 20 ms), waits for the interconnection to disconnect, and then restores to the original open-loop operation state before starting the fault judgment. Through this protection configuration strategy, fault isolation can be achieved without changing the action logic of the distribution automation.

[0014] Preferably, the specific implementation steps of the fault ride-through function are as follows: when a line fault occurs, the flexible interconnection device has a certain fault ride-through ability through its own device characteristics and corresponding control strategies to ensure continuous power supply to the non-faulty interconnection lines. When a fault occurs outside the interconnection line area, ensure that the interconnection equipment does not disconnect and maintain the line interconnection operation; when a fault occurs within the interconnection line area, the flexible interconnection device can accept the instructions of the distribution control master station and select whether to disconnect the interconnection device according to the actual fault location.

[0015] The present invention also includes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the optimization method for the asymmetric flexible interconnected AC-DC hybrid distribution network are realized.

[0016] Through advanced control technologies and algorithms, the present invention realizes the precise control and optimization of the power flow of the asymmetric flexible interconnected AC-DC hybrid distribution network, thereby improving the power supply stability and energy utilization efficiency of the distribution network. It can flexibly adjust the operation mode and power flow distribution according to different load demands and energy supply situations to achieve the optimal allocation of energy, and quickly adjust the operation mode of the interconnected system when a fault occurs in the distribution network to ensure the continuity and stability of power supply.

[0017] The above description of the invention content is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the following specific embodiments of the present invention are specifically given. Description of the Drawings

[0018] By reading the detailed description of the non-restrictive embodiments with reference to the following drawings, other features, purposes and advantages of the present invention will become more obvious. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0019] Figure 1It is the equivalent circuit of the distribution loop network in an asymmetric flexible interconnected AC / DC hybrid distribution network optimization method provided by an embodiment of the present invention.

[0020] Figure 2 It is the main circuit topology of the medium-voltage flexible interconnected system in an asymmetric flexible interconnected AC / DC hybrid distribution network optimization method provided by an embodiment of the present invention.

[0021] Figure 3 It is the schematic diagram of the parallel-side double-loop control system structure based on the stability of the AC bus voltage in an asymmetric flexible interconnected AC / DC hybrid distribution network optimization method provided by an embodiment of the present invention.

[0022] Figure 4 It is the schematic diagram of the series-side double-loop control system structure based on the regulation of line power flow in an asymmetric flexible interconnected AC / DC hybrid distribution network optimization method provided by an embodiment of the present invention.

[0023] Figure 5 It is the schematic diagram of the closed-loop voltage compensation characteristic curve when the line closed-loop function is realized by a flexible device in an asymmetric flexible interconnected AC / DC hybrid distribution network optimization method provided by an embodiment of the present invention.

[0024] Figure 6 It is the schematic diagram of the voltage compensation control system structure in an asymmetric flexible interconnected AC / DC hybrid distribution network optimization method provided by an embodiment of the present invention. Detailed implementation manners

[0025] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific implementation manners described herein are only the best embodiments of the present invention, which are only used to explain the present invention and do not limit the protection scope of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0026] Before discussing the exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts depict operations (or steps) as sequential processes, many of the operations (or steps) can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when its operations are completed, but it can also have additional steps not included in the drawings; the process can correspond to a method, function, procedure, subroutine, subprogram, and so on. The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present invention and the above drawings are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. It should also be understood that in various embodiments of the present invention, the magnitude of the serial numbers of the processes does not mean the order of execution, and the order of execution of the processes should be determined by their functions and internal logics, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0027] It should be understood that in the present invention, "a plurality of" means two or more. "And /

[0028] or" is merely a variable relationship describing associated objects, indicating that three relationships can exist. It should be understood that in the present invention, "B corresponding to A", "B corresponding to A relatively", "A corresponding to B", or "B corresponding to A" means that B is associated with A, and B can be determined according to A. Determining B according to A does not mean determining B only according to A, and B can also be determined according to A and / or other information. The matching of A and B means that the similarity between A and B is greater than or equal to a preset threshold.

[0029] The present invention includes an optimization method for an asymmetric flexible interconnected AC / DC hybrid distribution network. For a target distribution network object, the target distribution network object is monitored. First, it is judged whether the voltages on both sides are symmetric. When it is confirmed that the voltages on both sides are asymmetric and no abnormality occurs, a topological model of the monitoring object is established based on the topological structure of the flexible interconnection device, the optimization target is determined, and the constraint conditions are set; an optimization model is established, and a control strategy for implementing the optimization is selected according to the optimization model.

[0030] The voltage levels of asymmetric interconnection under research include various methods such as 6 / 10 kV interconnection, 10 / 20 kV interconnection, 6 / 20 kV interconnection, etc. However, considering the actual application scenarios and cost price factors, the form of 6 / 10 kV interconnection in the prior art has better application value. The present invention takes 6 / 10 kV interconnection as a specific embodiment for illustration:

[0031] Embodiment 1:

[0032] As shown Figure 1 in the equivalent circuit of the distribution ring network in the asymmetric state involved in the present invention, the voltages on both sides in this circuit are 6 kV and 10 kV respectively. V A represents the bus voltage; I A1 , I A2 respectively represent the currents of two feeders; V H represents the output voltage of the flexible interconnection device; S i represents the equivalent load of the i-th branch line; S A1 , S A2 respectively represent the output apparent powers of feeder 1 and feeder 2; Z m represents the impedance of the m-th section of the ring network line.

[0033] Before installing the flexible interconnection device, the output apparent powers of feeder 1 and 2 are:

[0034]

[0035] In the formula, Z ∑ =R ∑ +jX ∑ , represents the total impedance of the ring network including the system equivalent impedance.

[0036] After installing the flexible interconnection device, the change in the power flow of feeder 1 is:

[0037]

[0038] By adjusting the flexible interconnection device V H ∠β, the transmission power flow of the lines in the distribution ring network can be controlled. This is because, after installing the flexible closing device at the head end of feeder 1, it is equivalent to adding an additional auxiliary voltage source, which can generate a circulating current, making the distribution of current in the ring network more reasonable and also making the distribution of power flow in the ring network more reasonable. The medium-voltage flexible interconnection system connects two voltage source converters in a back-to-back form to the AC distribution line, and through the independent control of active and reactive power in the AC system, functions such as electromagnetic ring network disconnection and fault isolation are realized.

[0039] Figure 2 is the main circuit of the medium-voltage flexible interconnection system in this embodiment. Its core is the current source converter, which uses semiconductor devices with turn-off capabilities and pulse width modulation (PWM) technology, enabling the system to achieve closed-loop operation between multiple different distribution lines under normal operating conditions, rapid load transfer under fault conditions, realizing on-site reactive power compensation for the load while achieving seamless connection of each feeder, and precisely controlling the active and reactive powers of each port, thereby changing the power flow on the grid side, realizing power flow optimization control, and improving equipment utilization rate and power supply reliability.

[0040] After establishing the topological structure based on the flexible interconnection device, set the constraint conditions for power flow control, which consist of system constraint conditions and equipment parameter constraint conditions.

[0041] The system constraint conditions for the conventional optimal power flow are

[0042]

[0043]

[0044] In the formula: S B is the set of all nodes in the system; S G is the set of all generators; S R is the set of all reactive power sources; S l is the set of all branches; P Gi , Q Gi are the active and reactive power outputs of the generator at node i; P Di , Q Di are the active and reactive power loads at node i; U i , θ i are the voltage amplitude and phase angle of node i, and θ ij = θ i - θ j ; G ij , B ij are the real and imaginary parts of the node admittance matrix; P l is the active power flow of line l, and the two ends of line l are nodes i and j.

[0045] Equation (4) represents the node power balance equation, Equation (5) represents the active and reactive power output constraints of the power source and the node voltage constraint respectively, and Equation (6) represents the line power constraint.

[0046] The characteristic parameters of the flexible interconnection system need to be reasonably selected within the range of the performance limitations of each part of the equipment to ensure the best regulation effect on the line power.

[0047] System series part voltage and current constraints

[0048]

[0049] System parallel part voltage and current constraints

[0050]

[0051] Phase adjustment angle Range

[0052]

[0053] Set the system optimization objectives according to the different operating states of the 6 / 10 kV medium-voltage flexible interconnection system. The optimization objectives include balancing the line load rate and minimizing the active power loss of the line, and coordinating these two different optimization objectives.

[0054] When the load rate of the 6 kV or 10 kV line is too high, take balancing the line load rate as the optimization objective to minimize the maximum value of the line load rate. The line load rate is defined as follows:

[0055]

[0056] where (l ∈ S l ), P l is the active power of line l, and P lmax is the active power limit of line l.

[0057] The objective function for balancing the line load rate is

[0058] min[max f l (11)

[0059] This optimization objective sets limits on the load rates of each line, ensuring the balance of power on each line.

[0060] When the load rates of both the 6 kV and 10 kV lines are within a reasonable range, set minimizing the active power loss of the two-side lines as the optimization objective.

[0061] The magnitude of the active power flowing from node i to branch i-j is

[0062]

[0063] The magnitude of the active power received by node j from branch i-j is

[0064]

[0065] Therefore, the objective function for minimizing the active power loss is

[0066]

[0067] When the load rate of the 6 kV or 10 kV line is unreasonable, take balancing the line load rate as the optimization objective and the line active power loss as the constraint condition

[0068]

[0069] where is the upper limit of the active power loss.

[0070] When the load rate levels of 6 kV and 10 kV lines are both within a reasonable range, the minimization of active power losses on both sides of the line can be taken as the optimization goal, and the line load rate as the constraint condition

[0071] |P l | = |P ij | ≤ k l P lmax (16)

[0072] where k l is the maximum load rate set for each line.

[0073] Finally, according to the optimization model, a power flow control strategy for implementing optimization is selected:

[0074] Establish a mathematical model in the two-phase synchronous rotating dq coordinate system for the rectifier side and the inverter side of the converter:

[0075]

[0076] where the model of the shunt side is shown in Equation (17), u 1d and u 1q are the d-axis and q-axis components of the grid voltage respectively; i shd and i shq are the d-axis and q-axis components of the input current of the shunt side converter respectively; u shd and u shq are the d-axis and q-axis components of the three-phase voltage on the AC side of the shunt side converter respectively; the model of the series side is shown in Equation (18), u sed and u seq are the d-axis and q-axis components of the AC side of the series transformer respectively; i sed and i seq are the d-axis and q-axis components of the output current of the series side converter respectively; u 12d and u 12q are the d-axis and q-axis components of the output voltage of the series side converter respectively; the rectifier side aims to control the stability of the DC side bus voltage and the AC bus voltage; the inverter side aims to control the power flow of the line and adjust the voltage difference between the two ends of the bus; at the same time, feedforward compensation is carried out using the current feedback quantity, the grid disturbance quantity, and the resistance voltage drop, and the current controllers of the rectifier side and the inverter side are obtained as shown in Equations (19) and (20) respectively, where k p and k i represent the proportional and integral coefficients of the current controller of the converter.

[0077]

[0078] According to the above inner loop control equation, combined with the outer loop functions of the rectifier and inverter converters, the rectifier side aims to control the stability of the AC bus voltage and the DC bus voltage, and the inverter side aims to control the output of the specified power. The double-loop control block diagram of the rectifier and inverter sides is obtained as shown in the figure, where Figure 3 It is a parallel-side dual-loop control system based on AC bus voltage stability. Figure 4 It is a series-side double-loop control system based on line flow regulation.

[0079] By utilizing the characteristics of the rectifier and inverter sides, the output voltage of the series transformer can be controlled by receiving the power flow control power command issued by the dispatching system to achieve comprehensive optimization of the line:

[0080] When the load rate of the line on one side is high and the load rate of the line on the other side is low, the medium-voltage flexible interconnection system is remotely controlled to perform flow control, transfer the remaining capacity of the heavy-loaded line to the light-loaded line, and dynamically adjust according to the load conditions on both sides to balance the loads of the two lines, thereby improving the access capacity of distributed energy and diverse loads.

[0081] When the load surges on one side of the line, the voltage of the line on that side decreases; the medium-voltage flexible interconnection system uses power flow control to dynamically provide active and reactive support through the opposite line, so that the voltage returns to a reasonable range, thereby ensuring the stable operation of the distribution network.

[0082] Embodiment 2:

[0083] In the present invention, due to the inconsistency of line length, line transmission capacity, and load level on both sides of the distribution network, a voltage amplitude difference or phase difference will be generated at the closing position. If a direct closing is performed, it will cause an impact current to be generated in the line, which may cause the protection on the line to malfunction after the impact current is formed. The 6 / 10kV medium-voltage flexible interconnection system can reduce the impact current during closing and avoid malfunction of line protection through flexible closing. At the same time, the line flow can be transferred according to instructions after closing. Therefore, two methods can be used to reduce the closing impact current:

[0084] One is to monitor the voltage on both sides in real time and use the medium voltage flexible interconnection device to compensate for the voltage difference on both sides. When the voltage difference compensation is close to 0, close the loop switch to avoid the impact current. Figure 5 This solution needs to compensate for the travel time of circuit breaker closing and accurately predict voltage fluctuations to reduce the impact of inrush current.

[0085] Second, the leakage reactance of the series transformer is used to suppress the inrush current during loop closing. Monitor the voltage difference between the two substations. When the difference is within the range of the primary voltage of the series transformer, close the loop closing switch through local / remote operation. At this time, the inrush current of the line will be limited by the primary leakage reactance due to the open circuit of the secondary side of the series transformer. Since the primary leakage reactance is large, the inrush current can be effectively suppressed. This solution only needs to monitor the voltages on both sides and determine whether the voltages are within the safe operating range of the series transformer, without the need to control the converter, and the operation process is more controllable.

[0086] When the 6kV side line is under maintenance, power is supplied to the maintenance line by closing the tie switch and using the 10kV side power supply, which is called load transfer. When performing load transfer, the stability of the supply voltage needs to be considered. At this time, the 6 / 10kV medium-voltage flexible interconnection system operates in the DVR mode. By monitoring the difference between the actual grid voltage and the set voltage, this difference is used as the control target of the medium-voltage flexible interconnection device. The corresponding compensation voltage is output by the inverter side of the converter to keep the 6kV side voltage stable and ensure the power supply quality. As Figure 6 shown, it is the voltage compensation control system adopted when realizing the line loop closing function.

[0087] It should be noted that the optimized functions such as line flexible loop closing, power flow transfer, load transfer, fast disconnection, and fault ride-through achieved by the present invention are all realized based on the medium-voltage flexible interconnection device. There is no medium-voltage flexible interconnection device configured in the conventional AC distribution network, so it does not have the conditions to realize these functions.

[0088] The embodiment of the present invention also provides a computer device, which includes: a processor, a memory, and a computer program stored on the memory and executable on the processor. The processor calls the computer program stored in the memory and executes each step in the asymmetric flexible interconnection AC-DC hybrid distribution network optimization method provided in the embodiment of the present invention, and can achieve the same technical effects. Referring to the description in the above embodiments, it will not be repeated here.

[0089] It should be noted that those skilled in the art can understand that the electronic device in the embodiments of the present invention is a device capable of automatically performing numerical calculations and / or information processing according to pre-set or stored instructions, and its hardware includes but is not limited to microprocessors, application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), embedded devices, etc. The electronic device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The electronic device can perform human-computer interaction through means such as a keyboard, a mouse, a remote control, a touchpad, or a voice control device.

[0090] The embodiments of the present invention further provide a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements each process and step in the asymmetric flexible interconnected AC-DC hybrid distribution network optimization method provided by the embodiments of the present invention, and can achieve the same technical effects. To avoid repetition, it will not be elaborated here.

[0091] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of each embodiment of the above-mentioned asymmetric flexible interconnected AC-DC hybrid distribution network optimization method. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM, for short), etc.

[0092] The above specific implementation manners are the preferred implementation manners of an asymmetric flexible interconnected AC-DC hybrid distribution network optimization method of the present invention, and do not limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to this specific implementation manner. Any equivalent changes made according to the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. An optimization method for an asymmetric flexible interconnected AC-DC hybrid distribution network, which selects a target distribution network object, characterized in that, Monitor the target distribution network object. First, determine whether the voltages on both sides are symmetric. When it is confirmed that the voltages on both sides are asymmetric and no abnormality has occurred, establish a topological model of the monitoring object based on the topological structure of the flexible interconnection device, determine the optimization objectives, and set the constraint conditions; establish an optimization model, and select a control strategy for implementing the optimization according to the optimization model.

2. The optimization method of the asymmetric flexible interconnected AC-DC hybrid distribution network according to claim 1, characterized in that The flexible devices installed in the topological model include a flexible loop closing device installed at the head end of the feeder, and a medium-voltage flexible interconnection system formed by connecting two voltage source converters in a back-to-back form to the AC distribution line.

3. The optimization method of the asymmetric flexible interconnected AC-DC hybrid distribution network according to claim 1, characterized in that The optimization objectives include balancing the line load rate and minimizing the active power loss of the line, and coordinating these two different optimization objectives.

4. The optimization method of the asymmetric flexible interconnected AC / DC hybrid distribution network according to claim 1, wherein The control strategies for implementing the optimization include a line loop closing function without current impact, a power flow transfer function, a load transfer function, a fast disconnection function, and a fault ride-through function.

5. The optimization method of the asymmetric flexible interconnected AC / DC hybrid distribution network according to claim 4, characterized in that The specific implementation steps of the line loop closing function are as follows: Collect the voltages at both ends of the flexible interconnection system acquisition device, and combine with the soft loop closing control algorithm to calculate the voltage amplitude and angle that the interconnection equipment needs to compensate. After the voltage output by the flexible interconnection device is superimposed on the original voltage, it is closest to the voltage on the other side, achieving the optimization goal of minimizing the impact current during loop closing.

6. The optimization method of the asymmetric flexible interconnected AC-DC hybrid distribution network according to claim 4, characterized in that The specific implementation steps of the power flow transfer function are as follows: For the normal operation condition of the distribution network, receive relevant control instructions issued by the monitoring system or the distribution dispatching main station, and adjust the flow direction and magnitude of the active / reactive power flow between the flexible interconnection feeders to achieve the optimization goal of mutual assistance of power flow and reasonable distribution of power between different feeders.

7. The optimization method of the asymmetric flexible interconnected AC / DC hybrid distribution network according to any one of claims 4, characterized in that The specific implementation steps of the load transfer function are as follows: When a bus fault or planned maintenance condition occurs on one side of the distribution network and the flexible interconnection device receives a load transfer instruction from the distribution dispatching main station, compare the transfer power and the device power flow transfer capacity. When the transfer power does not exceed the device power flow transfer capacity, support both load transfer through the flexible interconnection device and load transfer through the bypass switch; when the transfer power exceeds the device transfer capacity, only support load transfer through the bypass switch to maintain the power supply to the non-faulty load on the faulty side.

8. The optimization method of the asymmetric flexible interconnected AC / DC hybrid distribution network according to claim 4, characterized in that The specific implementation steps of the fast disconnection function are as follows: When a short-circuit fault occurs, the flexible interconnection device disconnects the interconnection within the first reference time and returns to the radial open-loop operation state. At the same time, when a short-circuit fault occurs, the distribution automation delays for the second reference time, waits for the interconnection to disconnect, and then returns to the original open-loop operation state to start fault judgment.

9. The optimization method of the asymmetric flexible interconnected AC-DC hybrid distribution network according to claim 4, characterized in that The specific implementation steps of the fault ride-through function are as follows: When a line fault occurs, the flexible interconnection device has a certain fault ride-through ability through its own device characteristics and corresponding control strategies to ensure continuous power supply to the non-faulty interconnection lines. When a fault occurs outside the interconnection line area, ensure that the interconnection equipment does not disconnect and maintain the line interconnection operation; when a fault occurs within the interconnection line area, the flexible interconnection device can accept instructions from the distribution dispatching main station and select whether to disconnect the interconnection device according to the actual fault location.

10. An electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it realizes the steps of the optimization method of the asymmetric flexible interconnected AC / DC hybrid distribution network as described in any one of claims 1 to 8.

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