A control method and system for medium / low voltage AC-DC hybrid distribution network

Abstract

The application provides a control method and system for a medium / low voltage AC / DC hybrid distribution network, which comprises the following steps: determining network frame data of the medium / low voltage AC / DC hybrid distribution network; substituting the network frame data into a centralized optimization model suitable for a medium voltage AC / DC hybrid distribution network and a distributed optimization model suitable for a low voltage AC / DC hybrid distribution network, to obtain an optimal solution of network loss of the medium voltage AC / DC hybrid distribution network and power fluctuation of a low voltage substation area public connection point (PCC) node of the low voltage AC / DC hybrid distribution network; and determining a centralized and distributed collaborative control strategy of the medium / low voltage AC / DC hybrid distribution network according to the optimal solution, so as to control the medium / low voltage AC / DC hybrid distribution network by using the centralized and distributed collaborative control strategy. The application realizes collaborative control of the medium / low voltage AC / DC hybrid distribution network.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system analysis, and in particular to a control method and system for a medium / low voltage AC-DC hybrid distribution network. BACKGROUND

[0002] With the proportion of new energy equipment such as energy storage, electric vehicle charging piles and distributed power gradually rising in the distribution network, the volatility and uncertainty of new energy equipment make the voltage fluctuation and other power quality problems of the traditional AC distribution network more serious. Due to the advantages of large power supply capacity, low power loss, controllable power flow, and small environmental pollution, the DC distribution network has become a feasible method to alleviate the aggravation of power quality problems in the traditional AC distribution network. Maximizing the development and utilization of renewable energy, improving the efficiency of the distribution network, and building a future smart distribution network with a shared and equal hierarchical structure, a combination of centralization and distribution, multi-source complementary flexibility and controllability, and a high degree of integration of physical systems and information systems are one of the core problems in solving the global energy revolution.

[0003] The medium voltage distribution network has perfect communication, measurement and calculation capabilities, and is more suitable for centralized control method. The centralized controller processes the measurement information reported by each control unit, and after global calculation, the corresponding instructions are issued to each control unit. Compared with the medium voltage distribution network, the low voltage distribution network has the disadvantages of weak calculation ability, incomplete measurement data, and relatively weak communication system, and the low voltage distribution network with multiple new equipment elements is more suitable for distributed control. Some studies have proposed a "medium-low" two-layer control model, and the medium and low voltage distribution networks both establish centralized optimization control models to improve network loss and three-phase imbalance, and are solved by sequential quadratic programming and particle swarm optimization algorithm respectively. However, due to the randomness and intermittency of photovoltaic output, the low voltage AC-DC distribution network still has voltage fluctuation problems, and the time scale of photovoltaic output fluctuation is very short, usually in seconds and minutes. If the medium and low voltage AC-DC hybrid distribution network adopts a centralized control model, it is impossible to reduce the impact of the low voltage distribution network by simply improving the control algorithm, because the time interval of centralized control (generally 15min-1h) is much larger than the typical fluctuation time scale of photovoltaic (generally several seconds to several minutes); most low voltage distribution networks cannot meet the communication and calculation ability requirements, and the application scope of the centralized control strategy is limited. In addition, the low voltage AC-DC hybrid distribution network will affect the operation control of the medium voltage AC-DC hybrid distribution network, and the severe voltage fluctuation of the low voltage will be transmitted to the medium voltage distribution network through the public connection node, affecting the stable operation of the upper grid. If the medium and low voltage AC-DC hybrid distribution network adopts a distributed control model, it will cause a certain waste of resources, cannot realize the global optimization of the medium voltage distribution network, and reduce the economic efficiency of the medium voltage AC-DC distribution network. SUMMARY

[0004] To solve the above problems, the application provides a control method for a medium / low voltage AC-DC hybrid distribution network, which comprises the following steps:

[0005] The basic data of the medium / low voltage AC-DC hybrid distribution network is divided based on the basic data of the medium / low voltage AC-DC hybrid distribution network, and the network frame data of the medium / low voltage AC-DC hybrid distribution network is determined;

[0006] The network frame data is substituted into a centralized optimization model suitable for the medium voltage AC-DC hybrid distribution network and a distributed optimization model suitable for the low voltage AC-DC hybrid distribution network, and the optimal solution of the medium voltage AC-DC hybrid distribution network loss and the low voltage AC-DC hybrid distribution network low voltage area public connection point (PCC) node power fluctuation is obtained;

[0007] The centralized and distributed collaborative control strategy of the medium / low voltage AC-DC hybrid distribution network is determined according to the optimal solution, and when there is a difference between the measured power and the instruction action value of the medium / low voltage AC-DC hybrid distribution network public connection point (PCC) or the internal node of the low voltage AC-DC hybrid distribution network, the medium / low voltage AC-DC hybrid distribution network is controlled by the centralized and distributed collaborative control strategy;

[0008] The centralized and distributed collaborative control strategy comprises a power tracking strategy and a fluctuation suppression strategy for the medium voltage AC-DC hybrid distribution network distribution area public connection point (PCC), and a limited active and reactive power adjustable range for the low voltage AC-DC hybrid distribution network distribution area public connection point (PCC);

[0009] The centralized optimization model takes the minimum network loss of the medium voltage AC-DC hybrid distribution network as the optimization target;

[0010] The distributed optimization model takes the minimum low voltage area PCC node power fluctuation of the low voltage AC-DC hybrid distribution network as the optimization target.

[0011] Optionally, the medium / low voltage AC-DC hybrid distribution network is controlled by the centralized and distributed collaborative control strategy, which comprises the following steps:

[0012] The power tracking strategy for the medium voltage AC-DC hybrid distribution network distribution area public connection point (PCC) is used to perform power tracking control on the medium voltage AC-DC hybrid distribution network distribution area public connection point (PCC);

[0013] The fluctuation suppression strategy for the medium voltage AC-DC hybrid distribution network distribution area public connection point (PCC) is used to perform fluctuation suppression control on the medium voltage AC-DC hybrid distribution network distribution area public connection point (PCC);

[0014] The active and reactive power adjustable range of the PCC is limited, and the active and reactive power of the PCC of the low-voltage AC / DC hybrid distribution network distribution area is adjusted to the active and reactive power adjustable range of the PCC.

[0015] Optionally, the grid data includes at least one of the following: grid structure data, interconnection mode data, flexible device control mode data, and load and photovoltaic access parameters of the medium / low-voltage AC / DC hybrid distribution network.

[0016] Optionally, the establishment of the centralized optimization model includes:

[0017] According to the grid data of the medium-voltage AC / DC hybrid distribution network, the optimization target, the constraint condition and the optimization variable of the centralized optimization model are determined;

[0018] According to the optimization target, the objective function is established;

[0019] According to the objective function, the constraint condition and the optimization variable, the centralized optimization model is constructed;

[0020] The constraint condition includes at least one of the following: the objective function, the constraint condition and the optimization variable;

[0021] The constraint condition includes at least one of the following: voltage constraint, PCC active and reactive power change range constraint, and medium-voltage controllable device active and reactive power capacity constraint;

[0022] The optimization variable includes at least one of the following: medium-voltage photovoltaic, VSC and active / reactive power output of PCC.

[0023] Optionally, the objective function of the centralized optimization model is as follows:

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] Where: minimize is the minimum value of the objective function, f1, f2, and f3 are the objective functions, f1 is the network loss function, f2 is the difference function between the estimated and optimized active power at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, f3 is the difference function between the estimated and optimized reactive power at the PCC of the medium-voltage AC / DC hybrid distribution network, W1, W2, and W3 are the weights of f1, f2, and f3, respectively; sf1, sf2, and sf3 are the scaling factors corresponding to f1, f2, and f3, respectively, and P... loss For network loss, P load ,P DG , These represent the load at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, the active power of the distributed generation source and the voltage source converter (VSC), respectively, and Q. load Q DG , These represent the reactive power of the PCC load, distributed generation, and voltage source converter VSC in the medium-voltage AC / DC hybrid distribution network, respectively, with Δτ representing the unit time interval. and These are the estimated and optimized values ​​of active power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively. and These are the estimated and optimized values ​​of reactive power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively, where Φ is the node phase and i is the PCC label. For PCC sets in medium-voltage AC / DC hybrid distribution networks, This refers to the set of all nodes in a medium-voltage AC / DC hybrid distribution network. These are the AC side network loss, DC side network loss, and voltage source converter (VSC) loss in the medium-voltage AC / DC hybrid distribution network.

[0031] Optional, the establishment of a distributed optimization model includes:

[0032] Based on the network structure data of the low-voltage AC / DC hybrid distribution network, the optimization objective, constraints, and optimization variables of the distributed optimization model are determined.

[0033] Establish an objective function based on the optimization objective;

[0034] Based on the objective function, constraints, and optimization variables, construct a distributed optimization model;

[0035] The constraints include at least one of the following: voltage constraints, PCC active and reactive power variation range constraints, and active and reactive power capacity constraints of medium-voltage controllable equipment.

[0036] The optimization variables include at least one of the following: active power output of low-voltage residential photovoltaic, energy storage, and VSC.

[0037] Optionally, the voltage constraint is as follows:

[0038]

[0039] wherein: V is the network node voltage of the medium / low voltage AC / DC hybrid power grid, V th-OV Vmax is the upper limit of the network node voltage, V th-UV Vmax is the upper limit of the network node voltage;

[0040] The PCC active and reactive power change range constraints are as follows:

[0041]

[0042]

[0043] wherein: and PCC active and reactive power adjustable amount of the medium / low voltage AC / DC hybrid distribution network, respectively, and upper and lower limits of the PCC active power adjustable amount of the medium / low voltage AC / DC hybrid distribution network, respectively, and upper and lower limits of the PCC reactive power adjustable amount of the medium / low voltage AC / DC hybrid distribution network, respectively;

[0044] The active and reactive power capacity constraints of the medium voltage controllable device are as follows:

[0045]

[0046]

[0047]

[0048] wherein: and medium / low voltage AC / DC hybrid distribution network medium voltage photovoltaic grid-connected active and reactive power, respectively, and upper and lower limits of the medium / low voltage AC / DC hybrid distribution network medium voltage photovoltaic grid-connected active power, respectively, and upper and lower limits of the medium / low voltage AC / DC hybrid distribution network medium voltage photovoltaic grid-connected reactive power, respectively, and medium / low voltage AC / DC hybrid distribution network VSC transmission active and reactive power, respectively, maximum regulation capacity of the medium / low voltage AC / DC hybrid distribution network VSC.

[0049] Optionally, the objective function of the distribution optimization model is as follows:

[0050]

[0051] minimize is the minimum value of the objective function, P i is the active power of the i-th node of the low-voltage AC side of the low-voltage AC / DC hybrid distribution network, is the given optimization value.

[0052] In still another aspect, the present application further provides a control system for a medium / low-voltage AC / DC hybrid distribution network, comprising:

[0053] a data acquisition unit, which divides the basic data based on the basic data of the medium / low-voltage AC / DC hybrid distribution network, and determines the network frame data of the medium / low-voltage AC / DC hybrid distribution network;

[0054] a solving unit, which substitutes the network frame data into a centralized optimization model suitable for the medium-voltage AC / DC hybrid distribution network and a distribution optimization model suitable for the low-voltage AC / DC hybrid distribution network, and obtains the optimal solution of the network loss of the medium-voltage AC / DC hybrid distribution network and the power fluctuation of the low-voltage substation public connection point PCC node of the low-voltage AC / DC hybrid distribution network;

[0055] a control unit, which determines the centralized and distributed collaborative control strategy of the medium / low-voltage AC / DC hybrid distribution network according to the optimal solution, and controls the medium / low-voltage AC / DC hybrid distribution network in the centralized and distributed collaborative control strategy when there is a difference between the measured power and the instructed action value of the medium / low-voltage AC / DC hybrid distribution network public connection point PCC or internal node;

[0056] The centralized and distributed collaborative control strategy comprises a power tracking strategy and a fluctuation suppression strategy for the medium-voltage AC / DC hybrid distribution network distribution substation public connection point PCC, and a limited active and reactive power adjustable range for the low-voltage AC / DC hybrid distribution network distribution substation public connection point PCC.

[0057] The centralized optimization model takes the minimum network loss of the medium-voltage AC / DC hybrid distribution network as the optimization target.

[0058] The distribution optimization model takes the minimum power fluctuation of the low-voltage substation PCC node of the low-voltage AC / DC hybrid distribution network as the optimization target.

[0059] Optionally, the control unit controls the medium / low-voltage AC / DC hybrid distribution network in the centralized and distributed collaborative control strategy, which comprises:

[0060] A power tracking strategy for a PCC of a medium-voltage AC / DC hybrid distribution network is used to perform power tracking control on the PCC of the medium-voltage AC / DC hybrid distribution network.

[0061] A fluctuation suppression strategy for a PCC of a medium-voltage AC / DC hybrid distribution network is used to perform fluctuation suppression control on the PCC of the medium-voltage AC / DC hybrid distribution network.

[0062] A limited active and reactive power adjustable range of a PCC of a low-voltage AC / DC hybrid distribution network is used to adjust the active and reactive power of the PCC of the low-voltage AC / DC hybrid distribution network to the limited active and reactive power adjustable range of the PCC.

[0063] Optionally, the grid data includes at least one of the following: grid structure data, interconnection mode data, flexible device control mode data, and load and photovoltaic access parameters of the medium / low-voltage AC / DC hybrid distribution network.

[0064] Optionally, the system further includes a first modeling unit configured to:

[0065] According to the grid data of the medium-voltage AC / DC hybrid distribution network, an optimization objective, a constraint condition, and an optimization variable of a centralized optimization model are determined.

[0066] A target function is established according to the optimization objective.

[0067] A centralized optimization model is constructed according to the target function, the constraint condition, and the optimization variable.

[0068] The constraint condition includes at least one of the following: the target function, the constraint condition, and the optimization variable.

[0069] The constraint condition includes at least one of the following: a voltage constraint, a PCC active and reactive power change range constraint, and a medium-voltage controllable device active and reactive power capacity constraint.

[0070] The optimization variable includes at least one of the following: a medium-voltage photovoltaic, a VSC, and a PCC active / reactive power output.

[0071] Optionally, the target function of the centralized optimization model established by the first modeling unit is as follows:

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] Where: minimize is the minimum value of the objective function, f1, f2, and f3 are the objective functions, f1 is the network loss function, f2 is the difference function between the estimated and optimized active power at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, f3 is the difference function between the estimated and optimized reactive power at the PCC of the medium-voltage AC / DC hybrid distribution network, W1, W2, and W3 are the weights of f1, f2, and f3, respectively; sf1, sf2, and sf3 are the scaling factors corresponding to f1, f2, and f3, respectively, and P... loss For network loss, P load ,P DG , These represent the load at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, the active power of the distributed generation source and the voltage source converter (VSC), respectively, and Q. load Q DG , These represent the reactive power of the PCC load, distributed generation, and voltage source converter VSC in the medium-voltage AC / DC hybrid distribution network, respectively, with Δτ representing the unit time interval. and These are the estimated and optimized values ​​of active power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively. and These are the estimated and optimized values ​​of reactive power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively, where Φ is the node phase and i is the PCC label. For PCC sets in medium-voltage AC / DC hybrid distribution networks, This refers to the set of all nodes in a medium-voltage AC / DC hybrid distribution network. These are the AC side network loss, DC side network loss, and voltage source converter (VSC) loss in the medium-voltage AC / DC hybrid distribution network.

[0079] Optionally, the system further includes a second modeling unit, the second modeling unit being used for:

[0080] Based on the network structure data of the low-voltage AC / DC hybrid distribution network, the optimization objective, constraints, and optimization variables of the distributed optimization model are determined.

[0081] Establish an objective function based on the optimization objective;

[0082] Based on the objective function, constraints, and optimization variables, construct a distributed optimization model;

[0083] The constraints include at least one of the following: voltage constraints, PCC active and reactive variation range constraints, and active and reactive capacity constraints of medium-voltage controllable devices.

[0084] The optimization variables include at least one of the following: active output of low-voltage household photovoltaic, energy storage, and VSC.

[0085] Optionally, the voltage constraints are as follows:

[0086]

[0087] Wherein: V is a network node voltage of a medium / low-voltage AC / DC hybrid power grid, V th-OV V is an upper limit of a network node voltage allowed voltage, V th-UV V is an upper limit of a network node voltage allowed voltage;

[0088] The PCC active and reactive variation range constraints are as follows:

[0089]

[0090]

[0091] Wherein: and PCC active and reactive adjustable amounts of a medium / low-voltage AC / DC hybrid distribution network, and upper and lower limits of the PCC active adjustable amount of the medium / low-voltage AC / DC hybrid distribution network, and upper and lower limits of the PCC reactive adjustable amount of the medium / low-voltage AC / DC hybrid distribution network;

[0092] The active and reactive capacity constraints of the medium-voltage controllable device are as follows:

[0093]

[0094]

[0095]

[0096] Wherein: and active and reactive of medium / low-voltage AC / DC hybrid distribution network medium-voltage photovoltaic grid-connected, and upper and lower limits of the active of medium / low-voltage AC / DC hybrid distribution network medium-voltage photovoltaic grid-connected, and These are the upper and lower limits of reactive power for medium-voltage photovoltaic grid-connected systems in medium / low-voltage AC / DC hybrid distribution networks. and These refer to the active and reactive power transmission of VSC in medium / low voltage AC / DC hybrid distribution networks. This represents the maximum regulating capacity of the VSC in a medium / low voltage AC / DC hybrid distribution network.

[0097] Optionally, the objective function of the distributed optimization model established by the second modeling unit is as follows:

[0098]

[0099] Where: minimize is the minimum value of the objective function. Let φ be the active power of the i-th node φ on the low-voltage AC side of the low-voltage AC / DC hybrid distribution network. Given the optimal value.

[0100] In another aspect, the present invention also provides a computing device, comprising: one or more processors;

[0101] A processor is used to execute one or more programs;

[0102] When the one or more programs are executed by the one or more processors, a control method for a medium / low voltage AC / DC hybrid distribution network as described above is implemented.

[0103] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements a control method for a medium / low voltage AC / DC hybrid distribution network as described above.

[0104] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0105] The application provides a control method for a medium / low voltage AC-DC hybrid distribution network, which comprises the following steps: dividing basic data of the medium / low voltage AC-DC hybrid distribution network based on the basic data, and determining network frame data of the medium / low voltage AC-DC hybrid distribution network; substituting the network frame data into a centralized optimization model suitable for the medium voltage AC-DC hybrid distribution network and a distributed optimization model suitable for the low voltage AC-DC hybrid distribution network, so as to obtain an optimal solution of network loss of the medium voltage AC-DC hybrid distribution network and power fluctuation of a low voltage area public connection point (PCC) node of the low voltage AC-DC hybrid distribution network; determining a centralized and distributed collaborative control strategy of the medium / low voltage AC-DC hybrid distribution network according to the optimal solution, and controlling the medium / low voltage AC-DC hybrid distribution network by using the centralized and distributed collaborative control strategy when there is a difference between a measured power of a PCC of the medium / low voltage AC-DC hybrid distribution network or a node inside the low voltage AC-DC hybrid distribution network and an instruction action value; wherein the centralized and distributed collaborative control strategy comprises a power tracking strategy and a fluctuation suppression strategy for the PCC of the medium voltage AC-DC hybrid distribution network, and a limited active and reactive power adjustable range of the PCC of the low voltage AC-DC hybrid distribution network; the centralized optimization model takes the minimum network loss of the medium voltage AC-DC hybrid distribution network as an optimization target; and the distributed optimization model takes the minimum power fluctuation of the low voltage area PCC node of the low voltage AC-DC hybrid distribution network as an optimization target. The centralized optimization model and the distributed optimization model established by the application respectively take the minimum network loss of the medium voltage AC-DC hybrid distribution network and the minimum power fluctuation of the low voltage area PCC node of the low voltage AC-DC hybrid distribution network as optimization targets, the network frame structure and the like are considered in the process of establishing the model, and finally the control strategy obtained by solving the model realizes the collaborative control of the medium / low voltage AC-DC hybrid distribution network, eliminates the voltage fluctuation problem of the distribution network caused by the photovoltaic access, improves the photovoltaic consumption capacity, and provides a theoretical support for the stable and economic operation of the medium / low voltage AC-DC hybrid distribution network. BRIEF DESCRIPTION OF DRAWINGS

[0106] Figure 1 Flow chart of the method of the application;

[0107] Figure 2 Medium / low voltage AC-DC hybrid distribution network frame structure diagram of the embodiment of the method of the application;

[0108] Figure 3 Medium / low voltage collaborative control communication configuration diagram of the embodiment of the method of the application;

[0109] Figure 4 Medium / low voltage AC-DC distribution network control time scale configuration diagram of the embodiment of the method of the application;

[0110] Figure 5 Photovoltaic and load 24-hour output curve diagram of the embodiment of the method of the application;

[0111] Figure 6 PCC point A phase voltage variation curve comparison chart for the method embodiment of the application;

[0112] Figure 7 Structure diagram of the system of the application. DETAILED DESCRIPTION

[0113] Reference will now be made to the drawings to describe the exemplary embodiments of the present application in detail. The application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art. Like reference numerals refer to like elements throughout the specification. It will be understood that when an element is referred to as being "on" another element, it can be directly on the element or intervening elements can also be present. In addition, terms such as first and second are used herein when claiming certain embodiments of the present application and should not be construed as limiting the scope of the claims to the absolute first and seconds but as generic references to the first and second instances respectively of the referenced elements. The use of the terms "first", "second", "third", etc. does not limit the quantity and / or order of those elements. These terms are used only as labels to help identify particular meanin

[0114] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0115] The application aims at the problem that using a distributed control model for a medium / low voltage AC / DC hybrid distribution network causes certain resource waste and cannot achieve global optimization, thereby reducing the operation economy of the medium voltage AC / DC distribution network, and proposes a control method and system for the medium / low voltage AC / DC hybrid distribution network.

[0116] Embodiment 1

[0117] The application proposes a control method for a medium / low voltage AC / DC hybrid distribution network, as shown in the figure, which comprises the following steps: Figure 1

[0118] Step 1: dividing the basic data based on the basic data of the medium / low voltage AC / DC hybrid distribution network to determine the network frame data of the medium / low voltage AC / DC hybrid distribution network; wherein the network frame data comprises at least one of the following: network frame structure data, interconnection mode data, flexible device control mode data and load and photovoltaic access parameters of the medium / low voltage AC / DC hybrid distribution network;

[0119] Step 2: substituting the network frame data into a pre-established centralized optimization model suitable for the medium voltage AC / DC hybrid distribution network and a distributed optimization model suitable for the low voltage AC / DC hybrid distribution network to obtain the optimal solution of the medium voltage AC / DC hybrid distribution network loss and the low voltage AC / DC hybrid distribution network low voltage area public connection point PCC node power fluctuation;

[0120] ​Step 3, determine the centralized and distributed collaborative control strategy of the medium / low voltage AC-DC hybrid distribution network according to the optimal solution, and when there is a difference between the measured power and the instructed action value of the medium / low voltage AC-DC hybrid distribution network public connection point PCC or low voltage AC-DC hybrid distribution network internal node, control the medium / low voltage AC-DC hybrid distribution network by the centralized and distributed collaborative control strategy;

[0121] The centralized and distributed collaborative control strategy includes a power tracking strategy and a fluctuation suppression strategy for the power connection point PCC of the medium voltage AC-DC hybrid distribution network, and a limited active and reactive power adjustable range of the PCC for the low voltage AC-DC hybrid distribution network.

[0122] The centralized optimization model takes the minimum network loss of the medium voltage AC-DC hybrid distribution network as the optimization target.

[0123] The distributed optimization model takes the minimum power fluctuation of the low voltage PCC node of the low voltage AC-DC hybrid distribution network as the optimization target.

[0124] The specific implementation steps and analysis methods are as follows:

[0125] In step 1, the network frame data is analyzed and divided by analyzing the basic data of the medium / low voltage AC-DC hybrid distribution network, and the analysis results are used to determine the specific implementation steps as follows:

[0126] The analysis results of the medium / low voltage AC-DC hybrid distribution network frame structure are as follows:

[0127] The typical network frame structure of the medium / low voltage AC-DC hybrid distribution network is shown in Figure 2 The typical network frame structure has a 27-node AC-DC hybrid distribution network on the medium voltage side, including 12 nodes on the DC side and 13 nodes on the AC side, interconnected by two VSCs. The low voltage distribution area under the medium voltage node has three types: low voltage AC distribution area, low voltage DC distribution area, and low voltage AC-DC hybrid distribution area, corresponding to Figure 2 low voltage distribution networks under 13 nodes, 27 nodes, 22 nodes, and 23 nodes.

[0128] Among them, the low voltage AC-DC hybrid distribution network formed by connecting the 22-node and 23-node distribution areas is controlled as a whole when doing distributed control. The medium voltage and low voltage AC distribution networks have three-phase three-wire and three-phase four-wire frame structures respectively. The medium and low voltage DC distribution networks have a three-wire structure with one positive and one negative and one neutral line, as shown in Figure 2 The photovoltaic power station is connected to the medium voltage AC-DC hybrid distribution network, and the household photovoltaic and energy storage device is connected to the low voltage AC-DC hybrid distribution network. VSC1 maintains the stability of the DC voltage, and VSC2-VSC4 controls the active and reactive power on the AC side.

[0129] The analysis results of the control architecture for the medium / low voltage AC / DC distribution network are as follows:

[0130] The medium voltage AC / DC distribution network can solve a relatively complex control model, and the measurement and communication are relatively sound, and the global index such as network loss is relatively high. Therefore, the medium voltage distribution network adopts a centralized control mode, and the control time interval is relatively long. The low voltage distribution network has relatively less investment, and the solving ability of the control model is not strong, and the communication and measurement functions are weak, and generally only the installation nodes of the adjustable equipment have measurement and local communication capabilities. Therefore, the low voltage distribution network adopts a distributed control mode and has the ability of fast response.

[0131] The communication configuration of the medium / low voltage AC / DC distribution network is shown in Figure 3 The medium voltage adopts a centralized control strategy, the centralized controller processes the data of the whole network and sends action instructions to the subordinate areas, and the subordinate areas adjust the corresponding equipment according to the received action instructions, and feedback the measured data to the centralized controller.

[0132] It should be noted that Figure 3 The low voltage area type in The nodes of the low voltage distribution network control area only establish a communication relationship with the adjacent nodes to exchange measurement information and control instructions.

[0133] The medium / low voltage AC / DC distribution network medium voltage centralized control, low voltage distributed control layer and medium / low voltage information interaction will be described below.

[0134] (1) Medium voltage centralized control

[0135] Firstly, the medium / low voltage AC / DC distribution network medium voltage centralized control unit obtains the state information of each medium voltage node, including: the power information of the low voltage load and the household photovoltaic at the point of common coupling (PCC);

[0136] Secondly, the medium voltage distribution network takes the minimum network loss value as the objective function, and takes the active and reactive power of the medium voltage photovoltaic power station, VSC and PCC as the control variable to establish an optimization model and solve it;

[0137] Finally, the control instructions are transmitted to each medium voltage node.

[0138] It should be particularly noted that the medium voltage photovoltaic power station usually has certain active and reactive power control capability, and the active and reactive power at the grid connection point is usually stable, which can be regarded as no fluctuation disturbance.

[0139] (2) Low voltage distributed control layer

[0140] The low-voltage distribution network takes the suppression of node power fluctuation as an objective function, and establishes an optimization model and solves it with active and reactive power of low-voltage photovoltaic, energy storage and VSC as control variables.

[0141] (3) Medium and low voltage information interaction;

[0142] The information interaction hub of the medium and low voltage distribution network is PCC, and the implementation of the coordination mechanism needs to consider the cooperation of time scale and information transmission, Figure 4 is a schematic diagram of information interaction of the medium and low voltage distribution network under their respective time scales, which is divided into three steps:

[0143] ① The low-voltage distribution network uploads the power information of the low-voltage load and household photovoltaic at PCC and the active and reactive power adjustable range at PCC to the medium-voltage distribution network; ② The medium-voltage distribution network issues power regulation instructions to the low-voltage distribution network; ③ The low-voltage distribution network calculates the difference between the measured value and the instruction value of PCC, and once there is a difference between the measured power and the instruction action value of PCC or the internal nodes of the low-voltage distribution network, the distributed control is started to suppress the voltage fluctuation problem in the transformer area.

[0144] In step 2, the establishment process of the centralized optimization model suitable for the medium-voltage AC / DC hybrid distribution network and the distributed optimization model suitable for the low-voltage AC / DC hybrid distribution network is as follows:

[0145] The establishment of the centralized optimization model includes;

[0146] According to the network frame data of the medium-voltage AC / DC hybrid distribution network, the optimization objective, constraint condition and optimization variable of the centralized optimization model are determined;

[0147] According to the optimization objective, the objective function is established;

[0148] According to the objective function, constraint condition and optimization variable, the centralized optimization model is constructed;

[0149] The constraint condition includes at least one of the following: objective function, constraint condition and optimization variable;

[0150] The constraint condition includes at least one of the following: voltage constraint, PCC active and reactive power change range constraint, and active and reactive power capacity constraint of medium-voltage controllable equipment;

[0151] The optimization variable includes at least one of the following: active / reactive power output of medium-voltage photovoltaic, VSC and PCC.

[0152] The above centralized optimization model adopts decoupling method to decouple the calculation of AC / DC hybrid distribution network power flow;

[0153] The above centralized optimization model is as follows:

[0154] (1) Objective function, as follows:

[0155] The objective function of the centralized optimization model of the medium-voltage AC / DC hybrid power grid is:

[0156]

[0157]

[0158]

[0159]

[0160]

[0161]

[0162] where minimize is to find the minimum value of the function; f 1-3 is the objective function, f1 is the network loss function, f2 and f3 are the differences between the estimated values and the optimization results of the active (reactive) power of the PCC nodes, f2 and f3f3 aim to reduce the adjustment of the distributed energy storage, photovoltaic inverters and VSCs in the low-voltage distribution network; W1-3 are the weights of the three objective functions; sf 1-3 are the scale factors corresponding to the three objectives;

[0163] P loss is the network loss; P load ,P DG , are the active powers of the load, distributed power supply and VSC, respectively; Q load ,Q DG , are the reactive powers of the load, distributed power supply and VSC, respectively; Δτ is the unit time interval;

[0164] and are the estimated values and the optimization values of the active power of the PCC nodes, respectively, and are the estimated values and the optimization values of the reactive power, respectively; φ is the node phase, Φ = {A, B, C} represents the set of three phases; i is the node label, is the set of PCC nodes in the medium-voltage distribution network, which are connected to the low-voltage distribution network containing a high proportion of household photovoltaic power;

[0165] represents the set of all nodes in the medium-voltage distribution network;

[0166] are the AC side network loss, DC side network loss and VSC loss, respectively.

[0167] (2) Voltage constraints, as follows:

[0168] The optimization control model must ensure that the voltage of the network nodes is within the allowed range, as follows:

[0169]

[0170] wherein the upper limit of the allowed voltage of the network is V th-OV , and the lower limit of the allowed voltage of the network is V th-UV In the present application, the voltage limits of the AC side and the DC side are the same.

[0171] (4) PCC active and reactive power variation range constraints, as follows:

[0172] The adjustable active and reactive power capacity of the PCC is limited by the capacity of the adjustable equipment of the low-voltage distribution network, and therefore, the active and reactive power adjustment amount of the PCC should be limited, as follows:

[0173]

[0174]

[0175] wherein: and are the upper limit and the lower limit of the adjustable active power of the PCC, respectively, and the values are uploaded from the low-voltage distribution network to the medium-voltage distribution network before the execution of the medium-voltage optimization control; and are the upper limit and the lower limit of the adjustable reactive power of the PCC, respectively, and the values are uploaded from the low-voltage distribution network to the medium-voltage distribution network before the execution of the medium-voltage optimization control.

[0176] (5) Active and reactive power capacity constraints of the medium-voltage controllable equipment, as follows:

[0177] The active and reactive power equipment connected to the medium-voltage grid should also satisfy the equipment capacity constraints, as follows:

[0178]

[0179]

[0180]

[0181] wherein: and are the upper limit and the lower limit of the active power of the medium-voltage photovoltaic grid-connected equipment, respectively, and are the upper limit and the lower limit of the reactive power of the medium-voltage photovoltaic grid-connected equipment, respectively, and are the active power and the reactive power of the medium-voltage VSC, respectively, is the maximum adjustment capacity of the VSC.

[0182] The establishment of the distribution optimization model comprises:

[0183] According to the network frame data of the low-voltage AC-DC hybrid power distribution network, the optimization objective, the constraint condition and the optimization variable of the distribution optimization model are determined;

[0184] The objective function is established according to the optimization objective;

[0185] The centralized optimization model is constructed according to the objective function, the constraint condition and the optimization variable;

[0186] The constraint condition comprises at least one of the following: a voltage constraint, a PCC active and reactive power change range constraint and a medium-voltage controllable device active and reactive power capacity constraint;

[0187] The optimization variable comprises at least one of the following: a low-voltage household photovoltaic, energy storage and VSC active output.

[0188] The distribution optimization model is specifically as follows:

[0189] (1) The objective function is as follows:

[0190] The objective function of the low-voltage AC-DC optimization control model is as follows:

[0191]

[0192] In the formula: is the low-voltage AC side i node φ phase active power; is the given optimization value of the medium voltage.

[0193] (2) The voltage constraint, the PCC active and reactive power change range constraint and the medium-voltage controllable device active and reactive power capacity constraint in the constraint condition are the same as those of the centralized optimization model;

[0194] Further comprising: the device capacity constraint of the energy storage should be satisfied, and the formula is as follows:

[0195]

[0196] In the formula: and are the upper and lower limits of the energy storage active power; is the active output of the energy storage at τ moment.

[0197] The stable energy storage state of charge (SOC) change amount is denoted as In order to avoid overcharging / overdischarging of the energy storage, the SOC change of the energy storage should be further limited, and the limitation is as follows:

[0198]

[0199]

[0200]

[0201] In the formula: SOC is the state of charge of the energy storage at time t; SOC min and SOC max are the lower and upper limits of the SOC change range of the energy storage, respectively; C is the capacity of the energy storage.

[0202] The coordination of the medium / low voltage AC / DC distribution network is mainly reflected in the response and processing of the PCC power by the medium / low voltage control model. For low voltage distributed control, the control model can realize PCC power tracking and fluctuation suppression, which is conducive to reducing the operation and control difficulty of the medium voltage AC / DC distribution network and avoiding the medium voltage power quality problems caused by low voltage household photovoltaic fluctuation. For medium voltage centralized control, the control model considers the load and photovoltaic net power at the PCC ( and ), and limits the active and reactive power adjustable range of the PCC ( and ) fully considers the regulation ability of low voltage energy storage, photovoltaic and VSC.

[0203] The centralized optimization model and the distributed optimization model of the medium / low voltage AC / DC distribution network can be solved by using the cplex solver.

[0204] In step 3, the medium / low voltage AC / DC hybrid distribution network is controlled by using the centralized and distributed collaborative control strategy, including:

[0205] The power tracking strategy of the PCC of the medium voltage AC / DC hybrid distribution network is used to control the power tracking of the PCC of the medium voltage AC / DC hybrid distribution network.

[0206] The fluctuation suppression strategy of the PCC of the medium voltage AC / DC hybrid distribution network is used to control the fluctuation suppression of the PCC of the medium voltage AC / DC hybrid distribution network.

[0207] The active and reactive power adjustable range of the PCC of the low voltage AC / DC hybrid distribution network is limited, and the active and reactive power of the PCC of the low voltage AC / DC hybrid distribution network is adjusted to the active and reactive power adjustable range of the PCC.

[0208] The following verifies the present application:

[0209] The photovoltaic power stations connected to nodes 6, 9, 13 and 16 in the medium-voltage AC / DC hybrid distribution network can be regarded as PQ nodes for active and reactive power stability. A certain reactive power regulating unit is installed in the photovoltaic power stations, and the rated capacity of the photovoltaic power stations is 200 kW. The nodes 22 and 23 are connected to low-voltage AC / DC hybrid distribution areas, the low-voltage DC distribution area A includes six DC nodes, and the low-voltage distribution area B includes five AC nodes, five of which are connected to single-phase photovoltaic and energy storage. The installed capacity of the energy storage and photovoltaic units is 5 kW and 6 kW respectively, the rated capacity of the photovoltaic inverter is 7 kVA, and the rated capacity of the low-voltage VSC is 200 kW. The medium-voltage centralized control time interval is 1 hour, and the low-voltage distributed control time interval is 10 minutes.

[0210] The photovoltaic and load 24-hour output curves are shown in Figure 5

[0211] In order to compare the effect of the cooperative control strategy proposed in the application, three control schemes of the medium and low-voltage AC / DC hybrid distribution network are used for comparison, which are no control strategy, medium and low-voltage centralized control and medium and low-voltage centralized and distributed control strategy.

[0212] Table 1 is the simulation results of the network loss of the medium-voltage AC / DC hybrid distribution network under different control schemes. As can be seen from Table 1, the total loss of the medium-voltage distribution network in the medium and low-voltage AC / DC hybrid distribution network without any control is the highest, and the total loss of the medium-voltage distribution network adopting the centralized and distributed control mode is the smallest. Regardless of the control mode, the device loss of the flexible interconnection device VSC is about 2% of the total loss. The centralized and distributed control strategy effectively maintains the operation economy of the medium-voltage distribution network.

[0213] Table 1

[0214]

[0215] Figure 6 For the time period from 12:00 to 14:00, the voltage fluctuation diagram of the A-phase PCC node of the medium-voltage 22 node (23 node) under the centralized and distributed control strategy of the medium and low-voltage distribution network. The low-voltage is controlled every 10 minutes, and a total of 12 times are controlled within two hours.

[0216] As shown in Figure 6 , the PCC node voltage of the low-voltage distribution network without voltage control fluctuates obviously due to the uneven photovoltaic output at noon. At the same time, the voltage exceeds the upper limit at the time points of 12:30 and 12:50, which is due to the large photovoltaic output at noon, the reverse of the power flow in the low-voltage distribution area line, and further causes the problem of the PCC node voltage exceeding the upper limit. If the medium and low-voltage AC / DC hybrid distribution network adopts the centralized control strategy, i.e. the medium and low-voltage distribution networks are controlled every 1 hour, the photovoltaic fluctuation in a short time cannot be suppressed as Figure 6 ​The voltage fluctuation of the low-voltage distribution network is shown by the medium yellow curve. In order to suppress the voltage fluctuation problem of the low-voltage distribution network, the time scale of the voltage control in the low-voltage distribution network must be shortened. In contrast, the voltage fluctuation problem of the PCC node using the centralized and distributed control strategy is effectively alleviated. The medium-voltage distribution network provides a PCC node power reference value to the low-voltage distribution network through centralized optimization every hour, and then the low-voltage distribution network optimizes the equipment of the low-voltage distribution network every 10 minutes based on the reference value provided by the medium-voltage distribution network, so as to realize the power following of the PCC node of the low-voltage distribution network. After the node power is effectively controlled, the node voltage fluctuation is also correspondingly alleviated. The centralized and distributed control strategy mentioned in the application further controls the node voltage by controlling the power of the PCC node, and the effectiveness of the application is verified by an example.

[0217] Based on the same inventive concept, the application further provides a control system 200 for a medium / low-voltage AC / DC hybrid distribution network, as shown in the figure, comprising: Figure 7

[0218] A data acquisition unit 201 divides the basic data based on the basic data of the medium / low-voltage AC / DC hybrid distribution network, and determines the network frame data of the medium / low-voltage AC / DC hybrid distribution network. The network frame data includes at least one of the following: network structure data, interconnection mode data, flexible device control mode data, and load and photovoltaic access parameters of the medium / low-voltage AC / DC hybrid distribution network.

[0219] A solving unit 202 is used for substituting the network frame data into a pre-established centralized optimization model suitable for the medium-voltage AC / DC hybrid distribution network and a distributed optimization model suitable for the low-voltage AC / DC hybrid distribution network, to obtain an optimal solution of the network loss of the medium-voltage AC / DC hybrid distribution network and the power fluctuation of the PCC node of the low-voltage AC / DC hybrid distribution network.

[0220] A control unit 203 is used for determining a centralized and distributed collaborative control strategy of the medium / low-voltage AC / DC hybrid distribution network according to the optimal solution, and controlling the medium / low-voltage AC / DC hybrid distribution network in the centralized and distributed collaborative control strategy when there is a difference between the measured power and the instructed action value of the PCC or the internal node of the medium / low-voltage AC / DC hybrid distribution network.

[0221] The centralized and distributed collaborative control strategy includes a power tracking strategy and a fluctuation suppression strategy for the PCC of the medium-voltage AC / DC hybrid distribution network, and a limited active and reactive power adjustable range for the PCC of the low-voltage AC / DC hybrid distribution network.

[0222] The centralized optimization model takes the minimum network loss of the medium-voltage AC / DC hybrid distribution network as the optimization target.

[0223] ​The distribution optimization model takes the minimum power fluctuation of the low-voltage PCC node of the low-voltage AC-DC hybrid power distribution network as the optimization target.

[0224] The control unit 203 is configured to control the medium / low-voltage AC-DC hybrid power distribution network in a centralized distributed collaborative control strategy, and the control unit 203 comprises:

[0225] The power tracking strategy of the PCC of the medium-voltage AC-DC hybrid power distribution network is used to perform power tracking control on the PCC of the medium-voltage AC-DC hybrid power distribution network.

[0226] The fluctuation suppression strategy of the PCC of the medium-voltage AC-DC hybrid power distribution network is used to perform fluctuation suppression control on the PCC of the medium-voltage AC-DC hybrid power distribution network.

[0227] The adjustable range of active power and reactive power of the PCC of the low-voltage AC-DC hybrid power distribution network is limited to the adjustable range of active power and reactive power of the PCC of the low-voltage AC-DC hybrid power distribution network.

[0228] The system 200 further comprises a first modeling unit 204, and the first modeling unit 204 is configured to:

[0229] The optimization target, the constraint condition, and the optimization variable of the centralized optimization model are determined according to the network frame data of the medium-voltage AC-DC hybrid power distribution network.

[0230] The objective function is established according to the optimization target;

[0231] The centralized optimization model is constructed according to the objective function, the constraint condition, and the optimization variable.

[0232] The constraint condition comprises at least one of the following: the objective function, the constraint condition, and the optimization variable.

[0233] The constraint condition comprises at least one of the following: a voltage constraint, a PCC active power and reactive power change range constraint, and a medium-voltage controllable device active power and reactive power capacity constraint.

[0234] The optimization variable comprises at least one of the following: a medium-voltage photovoltaic device, a VSC, and a PCC active power / reactive power output.

[0235] The objective function of the centralized optimization model established by the first modeling unit 204 is as follows:

[0236]

[0237]

[0238]

[0239]

[0240]

[0241]

[0242] Where: minimize is the minimum value of the objective function, f1, f2, and f3 are the objective functions, f1 is the network loss function, f2 is the difference function between the estimated and optimized active power at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, f3 is the difference function between the estimated and optimized reactive power at the PCC of the medium-voltage AC / DC hybrid distribution network, W1, W2, and W3 are the weights of f1, f2, and f3, respectively; sf1, sf2, and sf3 are the scaling factors corresponding to f1, f2, and f3, respectively, and P... loss For network loss, P load ,P DG , These represent the load at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, the active power of the distributed generation source and the voltage source converter (VSC), respectively, and Q. load Q DG , These represent the reactive power of the PCC load, distributed generation, and voltage source converter VSC in the medium-voltage AC / DC hybrid distribution network, respectively, with Δτ representing the unit time interval. and These are the estimated and optimized values ​​of active power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively. and These are the estimated and optimized values ​​of reactive power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively, where Φ is the node phase and i is the PCC label. For PCC sets in medium-voltage AC / DC hybrid distribution networks, This refers to the set of all nodes in a medium-voltage AC / DC hybrid distribution network. These are the AC side network loss, DC side network loss, and voltage source converter (VSC) loss in the medium-voltage AC / DC hybrid distribution network.

[0243] System 200 further includes a second modeling unit 205, the second modeling unit 205 being used for:

[0244] Based on the network structure data of the low-voltage AC / DC hybrid distribution network, the optimization objective, constraints, and optimization variables of the distributed optimization model are determined.

[0245] Establish an objective function based on the optimization objective;

[0246] Based on the objective function, constraints, and optimization variables, a centralized optimization model is constructed.

[0247] The constraints include at least one of the following: voltage constraints, PCC active and reactive variation range constraints, and active and reactive capacity constraints of medium-voltage controllable devices;

[0248] The optimization variables include at least one of the following: active output of low-voltage household photovoltaic, energy storage, and VSC.

[0249] The voltage constraints are as follows:

[0250]

[0251] Wherein: V is the network node voltage of the medium / low-voltage AC / DC hybrid power grid, V th-OV V is the upper limit of the network node voltage allowed voltage, V th-UV V is the upper limit of the network node voltage allowed voltage;

[0252] The PCC active and reactive variation range constraints are as follows:

[0253]

[0254]

[0255] Wherein: and PCC active and reactive adjustable amounts of the medium / low-voltage AC / DC hybrid distribution network, and are the upper and lower limits of the PCC active adjustable amount of the medium / low-voltage AC / DC hybrid distribution network, and are the upper and lower limits of the PCC reactive adjustable amount of the medium / low-voltage AC / DC hybrid distribution network;

[0256] The active and reactive capacity constraints of the medium-voltage controllable device are as follows:

[0257]

[0258]

[0259]

[0260] Wherein: and are the medium / low-voltage AC / DC hybrid distribution network medium-voltage photovoltaic grid-connected active and reactive, and are the upper and lower limits of the medium / low-voltage AC / DC hybrid distribution network medium-voltage photovoltaic grid-connected active, and respectively are the upper limit and lower limit of the medium / low voltage AC / DC hybrid distribution network medium voltage photovoltaic grid-connected reactive power, and respectively are the VSC transmission active power and reactive power of the medium / low voltage AC / DC hybrid distribution network, is the maximum regulation capacity of the VSC of the medium / low voltage AC / DC hybrid distribution network.

[0261] Optionally, the objective function of the distribution optimization model established by the second modeling unit is as follows:

[0262]

[0263] Wherein: minimize is the minimum value of the objective function, is the active power of the i-th node φ phase of the low voltage AC side of the low voltage AC / DC hybrid distribution network, is the given optimization value.

[0264] Embodiment 3:

[0265] Based on the same inventive concept, the application further provides a computer device, which comprises a processor and a memory, the memory is used to store a computer program, the computer program comprises program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components and the like, which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are specifically suitable for loading and executing one or more instructions in the computer storage medium to implement a corresponding method flow or a corresponding function, so as to implement the steps of the control method for the medium / low voltage AC / DC hybrid distribution network in the above embodiment.

[0266] Embodiment 4:

[0267] Based on the same inventive concept, the present application also provides a storage medium, specifically a computer readable storage medium (Memory), which is a memory device in a computer device, used for storing programs and data. It can be understood that the computer readable storage medium here can include the built-in storage medium in the computer device, and of course can also include the extended storage medium supported by the computer device. The computer readable storage medium provides a storage space which stores the operating system of the terminal. Moreover, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer readable storage medium here can be a high-speed RAM memory, or a non-volatile memory such as at least one disk memory. One or more instructions stored in the computer readable storage medium can be loaded and executed by the processor to implement the steps of the control method for the medium / low voltage AC / DC hybrid distribution network in the above embodiment.

[0268] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0269] The present application is described with reference to flowcharts and / or block diagrams of the method, device (system), and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks Figure 1 The means for implementing the functions specified in one or more flows and / or blocks.

[0270] These computer program instructions can also be stored in a computer readable storage medium which can guide the computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer readable storage medium produce a product including instruction means, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocksFigure 1 the function specified in the one or more blocks.

[0271] These computer program instructions can also be loaded into computer or other programmable data processing devices, so that a series of operation steps are performed on the computer or other programmable data processing devices to generate computer-implemented processes, thus the instructions executed on the computer or other programmable data processing devices provide processes for implementing the flows Figure 1 the flows or the flows and / or blocks Figure 1 the steps of the function specified in the one or more blocks.

[0272] The above merely describes the embodiments of the present application, and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the scope of the claims of the present application.

Claims

1. A control method for a medium / low voltage AC / DC hybrid distribution network, characterized in that, The method includes: The basic data is divided based on the basic data of the medium / low voltage AC / DC hybrid distribution network to determine the network structure data of the medium / low voltage AC / DC hybrid distribution network; Substituting the network data into the pre-established centralized optimization model applicable to medium-voltage AC / DC hybrid distribution networks and the distributed optimization model applicable to low-voltage AC / DC hybrid distribution networks, the optimal solutions for network losses in medium-voltage AC / DC hybrid distribution networks and power fluctuations at the PCC nodes in low-voltage distribution areas of low-voltage AC / DC hybrid distribution networks are obtained. The centralized distributed cooperative control strategy for the medium / low voltage AC / DC hybrid distribution network is determined based on the optimal solution. When there is a difference between the measured power and the command action value of the common connection point (PCC) or the internal node of the medium / low voltage AC / DC hybrid distribution network, the centralized distributed cooperative control strategy is used to control the medium / low voltage AC / DC hybrid distribution network. The centralized distributed collaborative control strategy includes a power tracking strategy and a fluctuation suppression strategy for the distribution area common coupling point (PCC) of the medium-voltage AC / DC hybrid distribution network, and a strategy for limiting the active and reactive power adjustable range of the PCC for the distribution area common coupling point of the low-voltage AC / DC hybrid distribution network. The centralized optimization model takes minimizing the network loss of the medium-voltage AC / DC hybrid distribution network as its optimization objective. The distribution optimization model aims to minimize the power fluctuation of the PCC nodes in the low-voltage distribution area of ​​the low-voltage AC / DC hybrid distribution network.

2. The method according to claim 1, characterized in that, The medium / low voltage AC / DC hybrid distribution network is controlled using a centralized-distributed collaborative control strategy, including: The power tracking strategy of the distribution area common coupling point (PCC) of the medium-voltage AC / DC hybrid distribution network is used to perform power tracking control on the PCC of the distribution area of ​​the medium-voltage AC / DC hybrid distribution network. A fluctuation suppression strategy is used to control the fluctuation of the PCC (Point of Common Coupling) of the distribution area in the medium-voltage AC / DC hybrid distribution network. The active and reactive power of the PCC in the distribution area of ​​the low-voltage AC / DC hybrid distribution network is adjusted to the range of adjustable active and reactive power of the PCC within the specified range.

3. The method according to claim 1, characterized in that, The grid data includes at least one of the following: grid structure data, interconnection method data, flexible equipment control method data, and load and photovoltaic access parameters of the medium / low voltage AC / DC hybrid distribution network.

4. The method according to claim 1, characterized in that, The establishment of the centralized optimization model includes: Based on the network structure data of the medium-voltage AC / DC hybrid distribution network, the optimization objective, constraints, and optimization variables of the centralized optimization model are determined. Establish an objective function based on the optimization objective; Based on the objective function, constraints, and optimization variables, a centralized optimization model is constructed. The constraints include at least one of the following: objective function, constraints, and optimization variables; The constraints include at least one of the following: voltage constraints, PCC active and reactive power variation range constraints, and active and reactive power capacity constraints of medium-voltage controllable equipment. The optimization variables include at least one of the following: active / reactive output of medium-voltage photovoltaic, VSC, and PCC.

5. The method according to claim 4, characterized in that, The objective function of the centralized optimization model is as follows: Where: minimize is the minimum value of the objective function, f1, f2, and f3 are the objective functions, f1 is the network loss function, f2 is the difference function between the estimated and optimized active power at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, f3 is the difference function between the estimated and optimized reactive power at the PCC of the medium-voltage AC / DC hybrid distribution network, W1, W2, and W3 are the weights of f1, f2, and f3, respectively; sf1, sf2, and sf3 are the scaling factors corresponding to f1, f2, and f3, respectively, and P... loss For network loss, P load P DG , These represent the load at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, the active power of the distributed generation source and the voltage source converter (VSC), respectively, and Q. load Q DG , These represent the reactive power of the PCC load, distributed generation, and voltage source converter (VSC) in the medium-voltage AC / DC hybrid distribution network, respectively, with Δτ representing the unit time interval. and These are the estimated and optimized values ​​of active power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively. and Φ and i represent the estimated and optimized values ​​of reactive power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively, where Φ is the node phase and i is the PCC designation. For PCC sets in medium-voltage AC / DC hybrid distribution networks, This refers to the set of all nodes in a medium-voltage AC / DC hybrid distribution network. These are the AC side network loss, DC side network loss, and voltage source converter (VSC) loss in the medium-voltage AC / DC hybrid distribution network.

6. The method according to claim 1, characterized in that, The establishment of the distributed optimization model includes: Based on the network structure data of the low-voltage AC / DC hybrid distribution network, the optimization objective, constraints, and optimization variables of the distributed optimization model are determined. Establish an objective function based on the optimization objective; Based on the objective function, constraints, and optimization variables, construct a distributed optimization model; The constraints include at least one of the following: voltage constraints, PCC active and reactive power variation range constraints, and active and reactive power capacity constraints of medium-voltage controllable equipment. The optimization variables include at least one of the following: active power output of low-voltage residential photovoltaic, energy storage, and VSC.

7. The method according to claim 6, characterized in that, The voltage constraint is as follows: in: V represents the network node voltage of a medium / low voltage AC / DC hybrid power grid. th-OV V represents the upper limit of the allowable voltage for network nodes. th-UV This refers to the upper limit of the allowable voltage for network nodes. The constraints on the active and reactive power variation ranges of the PCC are as follows: in: and These refer to the active and reactive power adjustable values ​​at the point of common coupling (PCC) of the medium / low voltage AC / DC hybrid distribution network. and These are the upper and lower limits of the active power adjustable capacity at the point of common coupling (PCC) of medium / low voltage AC / DC hybrid distribution networks. and These are the upper and lower limits of the reactive power adjustable capacity of the point of common coupling (PCC) in medium / low voltage AC / DC hybrid distribution networks, respectively. The active and reactive power capacity constraints of the medium-voltage controllable equipment are given by the following formulas: in: and These represent the active and reactive power of medium-voltage photovoltaic grid-connected systems in a medium / low-voltage AC / DC hybrid distribution network. and These are the upper and lower limits of active power for medium-voltage photovoltaic grid-connected systems in medium / low-voltage AC / DC hybrid distribution networks. and These are the upper and lower limits of reactive power for medium-voltage photovoltaic grid-connected systems in medium / low-voltage AC / DC hybrid distribution networks. and These refer to the active and reactive power transmission of VSC in medium / low voltage AC / DC hybrid distribution networks. This represents the maximum regulating capacity of the VSC in a medium / low voltage AC / DC hybrid distribution network.

8. The method according to claim 6, characterized in that, The objective function of the distribution optimization model is as follows: Where: minimize is the minimum value of the objective function. Let φ be the active power of the i-th node φ on the low-voltage AC side of the low-voltage AC / DC hybrid distribution network. Given the optimal value.

9. A control system for a medium / low voltage AC / DC hybrid distribution network, characterized in that, The system includes: The data acquisition unit divides the basic data based on the basic data of the medium / low voltage AC / DC hybrid distribution network to determine the network structure data of the medium / low voltage AC / DC hybrid distribution network; The solution unit is used to substitute the network data into a pre-established centralized optimization model suitable for medium-voltage AC / DC hybrid distribution networks and a distributed optimization model suitable for low-voltage AC / DC hybrid distribution networks to obtain the optimal solutions for network losses in medium-voltage AC / DC hybrid distribution networks and power fluctuations at the PCC node in low-voltage distribution areas of low-voltage AC / DC hybrid distribution networks. The control unit is used to determine the centralized-distributed cooperative control strategy of the medium / low voltage AC / DC hybrid distribution network according to the optimal solution. When there is a difference between the measured power and the command action value of the common connection point (PCC) of the medium / low voltage AC / DC hybrid distribution network or the internal node of the low voltage AC / DC hybrid distribution network, the centralized-distributed cooperative control strategy is used to control the medium / low voltage AC / DC hybrid distribution network. The centralized distributed collaborative control strategy includes a power tracking strategy and a fluctuation suppression strategy for the distribution area common coupling point (PCC) of the medium-voltage AC / DC hybrid distribution network, and a strategy for limiting the active and reactive power adjustable range of the PCC for the distribution area common coupling point of the low-voltage AC / DC hybrid distribution network. The centralized optimization model takes minimizing the network loss of the medium-voltage AC / DC hybrid distribution network as its optimization objective. The distribution optimization model aims to minimize the power fluctuation of the PCC nodes in the low-voltage distribution area of ​​the low-voltage AC / DC hybrid distribution network.

10. The system according to claim 9, characterized in that, The control unit is used to control the medium / low voltage AC / DC hybrid distribution network using a centralized-distributed collaborative control strategy, including: The power tracking strategy of the distribution area common coupling point (PCC) of the medium-voltage AC / DC hybrid distribution network is used to perform power tracking control on the PCC of the distribution area of ​​the medium-voltage AC / DC hybrid distribution network. A fluctuation suppression strategy is used to control the fluctuation of the PCC (Point of Common Coupling) of the distribution area in the medium-voltage AC / DC hybrid distribution network. The active and reactive power of the PCC in the distribution area of ​​the low-voltage AC / DC hybrid distribution network is adjusted to the range of adjustable active and reactive power of the PCC within the specified range.

11. The system according to claim 9, characterized in that, The grid data includes at least one of the following: grid structure data, interconnection method data, flexible equipment control method data, and load and photovoltaic access parameters of the medium / low voltage AC / DC hybrid distribution network.

12. The system according to claim 9, characterized in that, The system further includes a first modeling unit, which is used for: Based on the network structure data of the medium-voltage AC / DC hybrid distribution network, the optimization objective, constraints, and optimization variables of the centralized optimization model are determined. Establish an objective function based on the optimization objective; Based on the objective function, constraints, and optimization variables, a centralized optimization model is constructed. The constraints include at least one of the following: objective function, constraints, and optimization variables; The constraints include at least one of the following: voltage constraints, PCC active and reactive power variation range constraints, and active and reactive power capacity constraints of medium-voltage controllable equipment. The optimization variables include at least one of the following: active / reactive output of medium-voltage photovoltaic, VSC, and PCC.

13. The system according to claim 12, characterized in that, The objective function of the centralized optimization model established by the first modeling unit is as follows: Where: minimize is the minimum value of the objective function, f1, f2, and f3 are the objective functions, f1 is the network loss function, f2 is the difference function between the estimated and optimized active power at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, f3 is the difference function between the estimated and optimized reactive power at the PCC of the medium-voltage AC / DC hybrid distribution network, W1, W2, and W3 are the weights of f1, f2, and f3, respectively; sf1, sf2, and sf3 are the scaling factors corresponding to f1, f2, and f3, respectively, and P... loss For network loss, P load P DG , These represent the load at the point of common coupling (PCC) of the medium-voltage AC / DC hybrid distribution network, the active power of the distributed generation source and the voltage source converter (VSC), respectively, and Q. load Q DG , These represent the reactive power of the PCC load, distributed generation, and voltage source converter (VSC) in the medium-voltage AC / DC hybrid distribution network, respectively, with Δτ representing the unit time interval. and These are the estimated and optimized values ​​of active power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively. and Φ and i represent the estimated and optimized values ​​of reactive power at the point of common coupling (PCC) of a medium-voltage AC / DC hybrid distribution network, respectively, where Φ is the node phase and i is the PCC designation. For PCC sets in medium-voltage AC / DC hybrid distribution networks, This refers to the set of all nodes in a medium-voltage AC / DC hybrid distribution network. These are the AC side network loss, DC side network loss, and voltage source converter (VSC) loss in the medium-voltage AC / DC hybrid distribution network.

14. The system according to claim 9, characterized in that, The system further includes a second modeling unit, the second modeling unit being used for: Based on the network structure data of the low-voltage AC / DC hybrid distribution network, the optimization objective, constraints, and optimization variables of the distributed optimization model are determined. Establish an objective function based on the optimization objective; Based on the objective function, constraints, and optimization variables, construct a distributed optimization model; The constraints include at least one of the following: voltage constraints, PCC active and reactive power variation range constraints, and active and reactive power capacity constraints of medium-voltage controllable equipment. The optimization variables include at least one of the following: active power output of low-voltage residential photovoltaic, energy storage, and VSC.

15. The system according to claim 14, characterized in that, The voltage constraint is as follows: in: V represents the network node voltage of a medium / low voltage AC / DC hybrid power grid. th-OV V represents the upper limit of the allowable voltage for network nodes. th-UV This refers to the upper limit of the allowable voltage for network nodes. The constraints on the active and reactive power variation ranges of the PCC are as follows: in: and These refer to the active and reactive power adjustable values ​​at the point of common coupling (PCC) of the medium / low voltage AC / DC hybrid distribution network. and These are the upper and lower limits of the active power adjustable capacity at the point of common coupling (PCC) of medium / low voltage AC / DC hybrid distribution networks. and These are the upper and lower limits of the reactive power adjustable capacity of the point of common coupling (PCC) in medium / low voltage AC / DC hybrid distribution networks, respectively. The active and reactive power capacity constraints of the medium-voltage controllable equipment are given by the following formulas: in: and These represent the active and reactive power of medium-voltage photovoltaic grid-connected systems in a medium / low-voltage AC / DC hybrid distribution network. and These are the upper and lower limits of active power for medium-voltage photovoltaic grid-connected systems in medium / low-voltage AC / DC hybrid distribution networks. and These are the upper and lower limits of reactive power for medium-voltage photovoltaic grid-connected systems in medium / low-voltage AC / DC hybrid distribution networks. and These refer to the active and reactive power transmission of VSC in medium / low voltage AC / DC hybrid distribution networks. This represents the maximum regulating capacity of the VSC in a medium / low voltage AC / DC hybrid distribution network.

16. The system according to claim 14, characterized in that, The objective function of the distributed optimization model established by the second modeling unit is as follows: Where: minimize is the minimum value of the objective function. Let φ be the active power of the i-th node φ on the low-voltage AC side of the low-voltage AC / DC hybrid distribution network. Given the optimal value.

17. A computer device, characterized in that, include: One or more processors; A processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the control method for a medium / low voltage AC / DC hybrid distribution network as described in any one of claims 1-8 is implemented.

18. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the control method for a medium / low voltage AC / DC hybrid distribution network as described in any one of claims 1-8.

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