Active power distribution network live load transfer day-before-day two-stage optimization control method and related device

Abstract

The invention discloses a day-ahead-intra-day two-stage optimization control method for live load transfer of an active power distribution network. The method comprises the following steps: constructing a day-ahead optimization operation model; calculating the maximum effective value of the loop closing impact current based on the day-ahead optimization operation model, and selecting a time period in which the maximum effective value of the loop closing impact current can meet the safety current of the electrical branch as an intra-day preparation loop closing time period; constructing an intra-day optimization control model; based on the intra-day optimization control model, calculating to obtain the maximum effective value of the intra-day loop closing impact current of the intra-day active power distribution network electrified load transfer electrical branch; if the calculated maximum effective value of the intra-day loop closing impact current meets the safety current requirement of the electrical branch, the live load transfer operation of the active power distribution network is executed in the intra-day loop closing preparation time period; theoretical reference can be provided for electrical operation personnel to execute live load transfer operation, the reliability and success rate of live load transfer operation of the active power distribution network are further improved, and the safe operation level of the power distribution network is improved.

Description

Technical Field

[0001] The invention relates to a closed-loop impulse current of live load transfer in an active distribution network, and in particular to a two-stage optimization control method for live load transfer in an active distribution network in the day before and within the day, and a related device. Background Art

[0002] "Closed-loop design, open-loop operation" is a power supply method commonly used in my country's distribution network. When the lines in the network need to be repaired or run at high load, the reliability of the power supply of the distribution network must be ensured by load transfer. The currently widely used load transfer method is "first on and then off", that is, the power is transferred after the loop is closed. During the closing process, the different voltage amplitudes and phases on both sides of the closing switch will cause the closing current to be generated. When the closing current is too large, it may further cause the overload of the equipment in the network, the tripping of the relay protection action, the failure of the closing operation, and in severe cases, a large number of loads will lose power.

[0003] In order to successfully close the loop, the closing current needs to be regulated. Currently, the most widely used methods in engineering are to adjust the transformer taps and the number of switched capacitors, or to adjust the grid operation mode in advance (the upper level closes the loop first), but the former is somewhat blind and the operation speed is slow, while the latter often only considers the safety of the closing loop and ignores the grid risks brought by the adjustment of the operation mode. In addition, there are also studies on regulating the closing process from the perspective of online adjustment of line switch protection parameters, but this requires no weak links in the grid line and has high requirements for the degree of grid automation and communication reliability. Summary of the invention

[0004] The purpose of the present invention is to solve the deficiencies of the above-mentioned prior art, thereby providing a two-stage optimization control method for active distribution network live load transfer before and during the day. The present invention proposes an active distribution network closed-loop short-circuit current calculation method that is adapted to the new power system, effectively simulates the size of the active distribution network live load transfer closed-loop impact current, reduces the risk of closed-loop transfer failure, improves the reliability, flexibility and economy of the active distribution network operation, reduces the risk of closed-loop transfer failure that may exist in the future, and improves the scientific leanness of power grid planning and the active operation control capability.

[0005] A two-stage optimization control method for transferring live loads in an active distribution network before and during the day, comprising the following steps:

[0006] S1. Based on the DC power flow constraint and aiming at the lowest system day-ahead operation cost, a day-ahead optimization operation model for active distribution network day-ahead load transfer in all periods is constructed;

[0007] S2. Based on the day-ahead optimization operation model, the day-ahead steady-state loop-closing impulse current amplitude and the maximum effective value of the loop-closing impulse current of the active distribution network with live load transferred to the electric gas branch are calculated, and the time period when the maximum effective value of the loop-closing impulse current can meet the safety current of the electric branch is selected as the intra-day preparatory loop-closing period;

[0008] S3. Considering the scheduling of flexible resources such as energy storage and based on DC power flow constraints, the daily optimization control model of active distribution network live load transfer day is constructed with the goal of minimizing the system's daily operating cost;

[0009] S4. Based on the intra-day optimization control model, the maximum effective value of the intra-day closed-loop impulse current of the active distribution network with live load transferred to the electric gas branch is calculated;

[0010] S5. If the maximum effective value of the intra-day closing-loop impulse current calculated by S4 meets the safety current requirement of the electrical branch, the active distribution network live load transfer operation is performed during the intra-day preparation closing-loop period; if it does not meet the requirement, the real-time charging and discharging power of the energy storage is adjusted by stepping, and then the process returns to step S4 to recalculate the intra-day closing-loop impulse current until it is met.

[0011] The day-ahead optimization operation model includes a first objective function with the lowest day-ahead operation cost of the system and a corresponding first constraint condition;

[0012] The first objective function:

[0013]

[0014] In the formula, is the electricity price of node a in period t in the day-ahead period, is the electric power of the generator set at node a during period t in the day-ahead phase;

[0015] The first constraint condition includes the power system equivalent DC operation constraint and the new energy output forecast constraint in the day-ahead stage. The power system equivalent DC operation constraint in the day-ahead stage includes the power node power conservation constraint, line transmission capacity constraint, generator output upper and lower limit constraint, generator ramp upper and lower limit constraint, and system phase angle operation constraint:

[0016]

[0017] In the formula, is the power generation power of photovoltaic unit m in the period t before the day, is the power generation of wind turbine n in period t the day before, is the phase angle of node i in period t before the day, is the phase angle of node j in period t a day ago, is the output of the mth generator set in the t-day period, is the output of the mth generator set in the period t-1 the day before, is the actual power consumption of load b during period t the day before, b ij is the susceptance parameter of branch ij, is the phase angle of node 1 of the power system at time t a day ago. Node 1 is set as a balanced node with a phase angle of 0. is the maximum transmission power corresponding to the distribution line ij, are the maximum limits of landslide and climbing power corresponding to generator set m respectively;

[0018] The current new energy output forecast constraints include wind power and photovoltaic output forecast constraints. The wind power output forecast constraints are as follows:

[0019]

[0020]

[0021] Where α is the correlation coefficient of surface roughness, v ref (t) is the wind speed measured by the fan, v is the theoretical wind speed, H ref H is the installation height of the wind measuring device DA is the actual height of the fan hub. ci is the wind turbine cut-in wind speed, v cr is the rated wind speed of the fan, v co is the maximum allowable wind speed, P r (v) is the wind turbine fitting output power curve, P r is the rated output power of the fan;

[0022] The photovoltaic output forecast constraint is as follows:

[0023]

[0024] In the formula, f pv is the rated energy conversion power of the photovoltaic array, P rate is the rated power generation of the photovoltaic array, A is the actual photovoltaic irradiance of the photovoltaic array; A s is the photovoltaic rated irradiance; α p is the power temperature coefficient; T STC is the test temperature of photovoltaic modules under standard test conditions, T is the actual temperature, is the real-time power of the photovoltaic power station, η4 is the conversion efficiency of solar energy to direct current, η inv is the inverter AC-DC conversion efficiency, A pv is the total area of ​​PV panels, Total solar radiation, is the abandoned light power of the PV power station in period t, is the rated power of the PV power station.

[0025] Based on the day-ahead optimization operation model, the day-ahead steady-state loop-closing impulse current amplitude and the maximum effective value of the loop-closing impulse current of the day-ahead active distribution network live load transferred to the power gas branch are calculated as follows:

[0026] In the S1 day-ahead optimization operation model, the new energy output, load forecast and distribution network topology parameters for the 24 hours the day before are input, and the day-ahead steady-state loop impact current amplitude of the active distribution network's live load transferred to the gas branch is calculated.

[0027] Based on the Thevenin equivalent circuit, the maximum value of the closed-loop impulse current is derived, and the formula is shown as follows:

[0028]

[0029] The Thevenin equivalent potential is are the amplitude and phase angle of the steady-state voltage difference at the closed loop obtained in the day-ahead stage, and the Thevenin equivalent impedance is expressed as Z eq =R eq +jωL eq ;

[0030] Solving formula (12) can obtain the expression of the day-ahead loop impact current:

[0031]

[0032] From the above formula, we can know that the closed-loop impulse current consists of a periodic component and a non-periodic component. The maximum value of the closing loop impact current before the day is:

[0033]

[0034] In the formula, is the impact coefficient, is the amplitude of the steady-state closed-loop impulse current the day before;

[0035] Furthermore, by integrating the first cycle of formula (13), the maximum effective value of the closed-loop impulse current within a day is obtained as follows:

[0036]

[0037] In the formula, It is the maximum effective value of the closed-loop impulse current within a day.

[0038] The intraday optimization control model includes a second objective function with the lowest intraday operating cost of the system and a corresponding second constraint condition;

[0039] The second objective function:

[0040]

[0041] In the formula, is the electricity price of node a in the next period of the day, is the electric power of the generator set at node a in the next period of the day. ES,RT is the equivalent charging and discharging price of the energy storage system in the next period of the day, p ES,RT is the charging and discharging power of the energy storage system in the next period of the day, N E It is an energy storage accessible node. is the charge and discharge energy of the kth energy storage at node i at time t;

[0042] The second constraint condition includes the equivalent DC operation constraint of the power system in the intraday stage and the optimal operation constraint of the energy storage system; the equivalent DC operation constraint of the power system in the intraday stage includes the power conservation constraint of the power node, the line transmission capacity constraint, the upper and lower limit constraints of the output of the generator set, the upper and lower limit constraints of the ramping of the generator set, and the phase angle operation constraint of the system:

[0043]

[0044] In the formula, is the power generation power of photovoltaic unit m during period t in a day, is the power generation of wind turbine n during period t in a day, is the phase angle of node i in period t within the day, is the phase angle of node j in period t within the day, is the output of the mth generator set during period t of the day, is the output of the mth generator set in the t-1 period of the day, is the actual power consumption of load b during period t in the day, b ij is the susceptance parameter of branch ij, is the phase angle of power system node i at time t within the day, node 1 is a balanced node, and the phase angle is 0, is the maximum transmission power corresponding to the distribution line ij, are the maximum limits of landslide and climbing power corresponding to generator set m respectively;

[0045] Considering the scheduling of flexible resources such as energy storage, the optimal operation constraints of the energy storage system are as follows:

[0046]

[0047] Where η ch , η dis SOC is the energy storage charging and discharging efficiency; k，t is the remaining energy of the kth energy storage at time t, SOC k，max and SOC k，minCorresponding to the maximum and minimum capacity of MES, SOC k，0 is the initial electrical energy.

[0048] Step S4 specifically includes the following steps:

[0049] The daily optimization control model inputs the parameters such as the new energy output of the active distribution network within one hour, load forecast, real-time charging and discharging power of energy storage, and distribution network topology, and calculates the daily steady-state closed-loop impact current amplitude of the active distribution network's live load transferred to the electricity and gas branch.

[0050] The maximum value of the closed-loop impact current within a day is derived according to the following formula:

[0051]

[0052] The Thevenin equivalent potential is are the amplitude and phase angle of the steady-state voltage difference at the closed loop obtained during the intraday period, and the Thevenin equivalent impedance is expressed as Z eq =R eq +jωL eq , solving formula (24) can obtain the expression of closed-loop impulse current:

[0053]

[0054] From the above formula, we can know that the closed-loop impulse current consists of a periodic component and a non-periodic component. The maximum instantaneous value of the intra-day closed-loop impact current is:

[0055]

[0056] In the formula, is the impact coefficient, is the daily steady-state closed-loop current amplitude;

[0057] Furthermore, by integrating the first cycle of formula (25), the maximum effective value of the closed-loop impulse current within a day is obtained as follows:

[0058]

[0059] In the formula, It is the maximum effective value of the closed-loop impulse current within a day.

[0060] The real-time charging and discharging power of energy storage is regulated by stepping, specifically:

[0061] The charging and discharging power step of the energy storage system is set to 0.1 times the charging and discharging power, as shown in the following formula:

[0062]

[0063] In the formula, is the unit step length of charge and discharge power, Maximum charge and discharge power.

[0064] A two-stage optimization control device for transferring live loads in an active distribution network before and during the day, comprising:

[0065] A day-ahead optimization operation model construction module, wherein the day-ahead optimization operation model is used to construct a day-ahead optimization operation model for the active distribution network for the entire period of day-ahead load transfer based on DC power flow constraints and with the goal of minimizing the day-ahead operation cost of the system;

[0066] A model for determining a preparatory closing period, wherein the model is used to calculate the day-ahead steady-state closing impulse current amplitude and the maximum effective value of the closing impulse current of the active distribution network with live load transferred to the electric gas branch based on the day-ahead optimization operation model, and select the time period when the maximum effective value of the closing impulse current can meet the safety current of the electric branch as the intra-day preparatory closing period;

[0067] An intraday optimization control model construction module, wherein the intraday optimization control model is used to consider the scheduling of flexible resources such as energy storage and to construct an intraday optimization control model for active distribution network live load transfer day based on DC power flow constraints with the goal of minimizing the system's intraday operating cost;

[0068] A closed-loop impulse current maximum effective value calculation module, which is used to calculate the maximum effective value of the closed-loop impulse current within a day when the live load of the active distribution network is transferred to the gas branch based on the intra-day optimization control model;

[0069] The transfer control module is used to perform the active distribution network live load transfer operation during the intra-day preparatory closing period when the calculated maximum effective value of the intra-day closing impact current meets the electrical branch circuit safety current requirement.

[0070] A computer device comprises a processor and a memory, wherein the memory stores a computer simulation program; the processor is capable of implementing the optimization control steps described in any one of the above schemes when executing the computer simulation program.

[0071] The beneficial effects of the present invention are as follows: compared with the prior art, the present invention proposes a method for calculating the short-circuit current of an active distribution network loop that is adapted to a new power system by constructing a two-stage optimization control model of load transfer in an active distribution network under a multi-energy form, which effectively simulates the magnitude of the impact current of the active distribution network's live load transfer loop, reduces the risk of loop transfer failure, improves the reliability, flexibility and economy of the active distribution network's operation, reduces the risk of loop transfer failure that may exist in the future, and improves the scientific and lean nature of power grid planning and the ability to actively control and manage operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 A flow chart of a two-stage optimization control scheme for the day-ahead and day-intraday transfer of live loads in an active distribution network provided by an embodiment of the present invention;

[0073] Figure 2 A schematic diagram of live load transfer in an active power distribution network provided by an embodiment of the present invention;

[0074] Figure 3 The day-ahead load distribution of the active distribution network provided by the embodiment of the present invention;

[0075] Figure 4 The wind power and photovoltaic power output curves for all periods of the day before provided by the embodiment of the present invention;

[0076] Figure 5 The maximum effective value operation result of the closed-loop impulse current of the branch 12-22 in all periods of the day before is provided by the embodiment of the present invention;

[0077] Figure 6 A waveform diagram of the closed-loop impulse current of the branch 12-22 at 11 o'clock in the day provided by an embodiment of the present invention;

[0078] Figure 7 The maximum effective value operation result of the closed-loop impulse current of the branch 25-29 in all periods of the day before is provided by the embodiment of the present invention;

[0079] Figure 8 A waveform diagram of the closed-loop impulse current of the branch 25-29 in one period of the day provided by the embodiment of the present invention;

[0080] Fig. 9 This is a diagram showing the maximum effective value control effect of the closed-loop impulse current of the branches 25-29 provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0081] The embodiment of the present invention provides a two-stage optimization control scheme for active distribution network live load transfer before and during the day, which is used to solve the problem of load transfer failure caused by live closing operation of active distribution network and improve the safety level of power grid operation. This scheme can effectively simulate the size of the ring-closing impact current of live load transfer of active distribution network, reduce the risk of closing transfer failure, and has strong feasibility.

[0082] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0083] A first aspect of the present invention provides a two-stage optimization control method for transferring live loads in an active distribution network before and during the day, the method comprising the following steps:

[0084] S1. Constructing a full-time optimization operation model for the day-ahead load transfer of the active distribution network based on DC power flow constraints. The optimization operation model includes a first objective function with the lowest day-ahead operation cost of the system and a corresponding first constraint condition.

[0085] S2. Input the parameters such as the new energy output, load forecast and distribution network topology of the previous 24 hours into the S1 model, calculate the steady-state closing-loop impact current of the live load of the active distribution network transferred to the electric gas branch, calculate the maximum effective value of the closing-loop impact current based on the Thevenin equivalent circuit, and select the time period when the maximum effective value of the closing-loop impact current can meet the safety current of the electrical branch as the preparatory closing-loop period within the day.

[0086] S3. Considering the scheduling of flexible resources such as energy storage, an intraday optimization control model for active distribution network load transfer is constructed based on DC power flow constraints. The optimization control model includes a second objective function with the lowest system daily operating cost and a corresponding second constraint condition.

[0087] S4 uses the S3 model to input parameters such as the new energy output of the active distribution network within one hour, load forecast, real-time charging and discharging power of energy storage, and distribution network topology, and calculates the maximum effective value of the impact current of the active distribution network's live load transferred to the gas branch circuit during the day.

[0088] If the maximum effective value of the closed-loop impact current calculated by S4 meets the safety current requirement of the electrical branch, S5 executes the live load transfer operation of the active distribution network; if not, the real-time charging and discharging power of the energy storage is adjusted by stepping, and the intraday optimization control model of S3 is returned to recalculate the maximum effective value of the closed-loop impact current until it is met.

[0089] The first objective function:

[0090]

[0091] In the formula, is the electricity price of node a in period t in the day-ahead period, is the electric power of the generator set at node a during period t in the day-ahead phase.

[0092] The first constraint condition includes the power system equivalent DC operation constraint (DC power flow constraint) and the new energy output forecast constraint. Among them, the power system equivalent DC model operation constraint includes power node power conservation constraint, line transmission capacity constraint, generator output upper and lower limit constraint, generator ramp upper and lower limit constraint, and system phase angle operation constraint:

[0093]

[0094] In the formula, is the power generation power of photovoltaic unit m during period t, is the power generation of wind turbine n during period t, is the phase angle of node i in period t before the day, is the phase angle of node j in period t a day ago, is the output of the mth generator set in the t-day period, is the output of the mth generator set in the period t-1 the day before, is the actual power consumption of load b during period t, in MW, b ij is the susceptance parameter of branch ij, is the phase angle of node 1 of the power system at time t. Node 1 is set as a balanced node with a phase angle of 0. is the maximum transmission power corresponding to the distribution line ij, are the maximum landslide and climbing power limits corresponding to generator set m respectively.

[0095] The current new energy output forecast model constraints include wind power and photovoltaic output forecast model constraints. The wind power output model constraints are as follows:

[0096]

[0097] Where α is the correlation coefficient of surface roughness, v ref (t) is the measured wind speed of the fan, H ref H is the installation height of the wind measuring device DA is the actual height of the fan hub. ci is the wind turbine cut-in wind speed, v cr is the rated wind speed of the fan, in m / s, Pr (v) is the wind turbine fitting output power curve, P r is the rated output power of the wind turbine, in MW.

[0098] The constraints of the photovoltaic output prediction model are as follows:

[0099]

[0100] In the formula, f pv is the rated energy conversion power of the photovoltaic array, P rate is the rated power of the photovoltaic array, in MW, and A is the actual photovoltaic irradiance, in MW / m 2 ; A s is the photovoltaic rated irradiance, in units of 1kW / m 2 ; α p is the power temperature coefficient; T STC It is the test temperature of photovoltaic modules under standard test conditions. is the real-time power of the photovoltaic power station, η4 is the conversion efficiency of solar energy to direct current, η inv is the inverter AC-DC conversion efficiency, A pv is the total area of ​​PV panels, Total solar radiation, is the abandoned light power of the PV power station in period t, is the rated power of the PV power station.

[0101] Based on the day-ahead optimization operation model, the day-ahead steady-state loop-closing impulse current amplitude and the maximum effective value of the loop-closing impulse current of the day-ahead active distribution network with live load transferred to the power gas branch are calculated as follows:

[0102] In the S1 model, the parameters such as the new energy output, load forecast and distribution network topology in the previous 24 hours are input to calculate the steady-state closed-loop current amplitude of the active distribution network live load transferred to the electricity and gas branch.

[0103]

[0104] Based on the Thevenin equivalent circuit, the maximum effective value of the closed-loop impulse current is derived. According to the Thevenin equivalent circuit, the time domain attenuation component of the closed-loop impulse current can be calculated, and then the maximum value of the closed-loop impulse current can be obtained. The calculation formula is shown as follows:

[0105]

[0106] The Thevenin equivalent potential is are the amplitude and phase angle of the steady-state voltage difference at the closed loop obtained in the day-ahead stage, and the Thevenin equivalent impedance is expressed as Z eq =Req +jωL eq Solving formula (12) yields the closed-loop impulse current expression:

[0107]

[0108] From the above formula, we can know that the closed-loop impulse current consists of a periodic component and a non-periodic component. When there is a maximum value of the closing loop impact current:

[0109]

[0110] In the formula, is the impact coefficient, is the amplitude of steady-state closed-loop impulse current within a day;

[0111] Furthermore, by integrating the first cycle of formula (13), the maximum effective value of the day-ahead loop impact current is obtained as follows:

[0112]

[0113] In the formula, It is the maximum effective value of the current of the closed loop impulse current a few days ago.

[0114] The second objective function:

[0115]

[0116] In the formula, is the electricity price of node a in the next period of the day, is the electric power of the generator set at node a in the next period of the day. ES,RT is the equivalent charging and discharging price of the energy storage system in the next period of the day, p ES,RT is the charging and discharging power of the energy storage system in the next period of the day, N E It is an energy storage accessible node. is the charge and discharge energy of the kth energy storage at node i at time t;

[0117] The second constraint condition includes the power system equivalent DC operation constraint (DC power flow constraint) and the energy storage system optimization operation constraint. The equivalent DC operation constraint of the power system in the intraday stage is as follows:

[0118]

[0119] In the formula, is the power generation power of photovoltaic unit m during period t in a day, is the power generation of wind turbine n during period t in the day, and the actual power of load b is the actual power consumption of load b during period t in the day, in MW, bij is the susceptance parameter of branch ij, is the phase angle of power system node i at time t within the day, Node 1 is a balanced node with a phase angle of 0. is the maximum transmission power corresponding to the distribution line ij, are the maximum landslide and climbing power limits corresponding to generator set m respectively.

[0120] Considering the scheduling of flexible resources such as energy storage, the optimal operation constraints of the energy storage system are as follows:

[0121]

[0122] Where η ch , η dis SOC is the energy storage charging and discharging efficiency; k，t is the remaining energy of the kth energy storage at time t, SOC k，max and SOC k，min Corresponding to the maximum and minimum capacity of MES, SOC k，0 is the initial electrical energy.

[0123] Step S4 specifically includes the following steps:

[0124] The S3 model is used to input the parameters of the active distribution network's new energy output, load forecast, real-time charging and discharging power of energy storage, and distribution network topology within one hour of the day, and the daily steady-state closed-loop impact current amplitude of the active distribution network's live load transferred to the gas branch is calculated.

[0125] The maximum value of the closed-loop impulse current within a day is derived from the following formula:

[0126]

[0127] The Thevenin equivalent potential is are the amplitude and phase angle of the steady-state voltage difference at the closed loop obtained during the intraday period, and the Thevenin equivalent impedance is expressed as Z eq =R eq +jωL eq Solving formula (24) yields the closed-loop impulse current expression:

[0128]

[0129] From the above formula, we can know that the closed-loop impulse current consists of a periodic component and a non-periodic component. When there is a maximum value of the closing loop impact current:

[0130]

[0131] In the formula, is the maximum value of the closed-loop impulse current within a day, is the impact coefficient, is the daily steady-state closed-loop current amplitude.

[0132] Furthermore, by integrating the first cycle of formula (25) (the operating frequency of the power system is 50 Hz, so one cycle is 0.02 seconds), the maximum effective value of the closed-loop impulse current is obtained as follows:

[0133]

[0134] In the formula, It is the maximum effective value of the closed-loop impulse current within a day.

[0135] The real-time charging and discharging power of energy storage is regulated by stepping, specifically:

[0136] The charging and discharging power step of the energy storage system is set to 0.1 times the charging and discharging power, as shown in the following formula:

[0137]

[0138] In the formula, is the unit step length of charge and discharge power, Maximum charge and discharge power.

[0139] After real-time energy storage charging and discharging power regulation, when the maximum effective value of the intraday closed-loop impact current can meet the electrical branch circuit safety current requirements, the stepping is stopped and the current energy storage charging and discharging power value is output.

[0140] A second aspect of the present invention provides a two-stage optimization control device for transferring live loads in an active distribution network before and during the day, comprising:

[0141] A day-ahead optimization operation model construction module, wherein the day-ahead optimization operation model is used to construct a day-ahead optimization operation model for the active distribution network for the entire period of day-ahead load transfer based on DC power flow constraints and with the goal of minimizing the day-ahead operation cost of the system;

[0142] A model for determining a preparatory closing period, wherein the model is used to calculate the day-ahead steady-state closing impulse current amplitude and the maximum effective value of the closing impulse current of the active distribution network with live load transferred to the electric gas branch based on the day-ahead optimization operation model, and select the time period when the maximum effective value of the closing impulse current can meet the safety current of the electric branch as the intra-day preparatory closing period;

[0143] An intraday optimization control model construction module, wherein the intraday optimization control model is used to consider the scheduling of flexible resources such as energy storage and to construct an intraday optimization control model for active distribution network live load transfer day based on DC power flow constraints with the goal of minimizing the system's intraday operating cost;

[0144] A closed-loop impulse current maximum effective value calculation module, which is used to calculate the maximum effective value of the closed-loop impulse current within a day when the live load of the active distribution network is transferred to the gas branch based on the intra-day optimization control model;

[0145] The transfer control module is used to perform the active distribution network live load transfer operation during the intra-day preparatory closing period when the calculated maximum effective value of the intra-day closing impact current meets the electrical branch circuit safety current requirement.

[0146] The third aspect of the present invention provides a computer device, comprising a processor and a memory, characterized in that the memory stores a computer simulation program; the processor is capable of implementing the two-stage optimization control method described in the above scheme when executing the computer simulation program.

[0147] In order to enable those skilled in the art to better understand the present invention and the advantages of the present invention, the following explanation is given in conjunction with the specific embodiments of the present invention:

[0148] The simulation hardware is an Intel(R) Core(TM) i7-11400 CPU@2.90GHz desktop computer. The simulation platform is Matlab R2024a platform calling cplex optimization software. Figure 2 The following is a schematic diagram of the active power distribution network with live load transfer provided by the embodiment of the present invention, wherein the dotted line branch represents the transfer branch. The parameters of the electrical branch of the active power distribution network are shown in Table 1, and the load distribution is shown in Table 1. Figure 3 As shown in Figure 2, wind power and photovoltaic access nodes and output are as follows: Figure 4 The parameters of the generator set are shown in Table 2, and the operating parameters of the energy storage system are shown in Table 3.

[0149] Table 1

[0150]

[0151]

[0152]

[0153] Table 2

[0154]

[0155] Table 3

[0156]

[0157]

[0158] Example 1: Select branch 12-22 to perform live load transfer operation.

[0159] In the first step, at the day-ahead stage, branches 12-22 are selected as the closed-loop branches. By running the full-time optimization operation model of the day-ahead load transfer, the maximum effective value distribution of the closed-loop impulse current during the full-time period is calculated as follows: Figure 5 As shown, it can be seen that the maximum effective value of the closing-loop impact current generated in time period 11 is the smallest, which is 247.40A. Therefore, time period 11 of the next day is selected as the pre-arranged time period for closing-loop operation.

[0160] The second step is to execute the active distribution network load transfer intraday optimization control model before the closing operation at 11:00 in the intraday stage, and the waveform of the maximum effective value of the closing impulse current of branch 12-22 is as follows: Figure 6 As shown. It can be seen that at this time, the maximum impact current (i.e. amplitude) of the closing loop branch is 508.56A, and the maximum effective value of the impact current is 311.47A, which is less than the maximum control current of branch 12-22, 521A. The closing loop current meets the intraday safety check and the closing loop operation can be performed.

[0161] Example 2: Select branch 25-29 to perform live load transfer operation.

[0162] In the first step, at the day-ahead stage, branches 25-29 are selected as the closing branches. By running the full-time optimization operation model of the day-ahead load transfer, the maximum effective value distribution of the closing impulse current during the full-time period is calculated as follows: Figure 7 As shown, it can be seen that the maximum effective value of the loop-closing impulse current generated in period 1 is the smallest, which is 468.68 A. Therefore, period 11 is selected as the pre-arranged period for the loop-closing operation a day ago.

[0163] In the second step, at 11:00 in the intraday stage, the intraday optimization control model of active distribution network live load transfer is executed, and the waveform of the maximum effective value of the closed-loop impulse current of branch 25-29 is obtained as follows: Figure 8 As shown, at this time, the maximum impact current of the closed-loop branch is 865.39A, and the maximum effective impact current is 530.01A, which is greater than the maximum control current of branch 25-29, 521A. The intra-day safety check of the closed-loop current is not met, so the energy storage real-time charging and discharging power control module is returned to control the closed-loop impact current by calling the energy storage system.

[0164] In the third step, the charging and discharging power step operation of the energy storage system is performed with a control step length of 2.5MW. The distribution of the maximum effective value of the closed-loop impact current is as follows: Fig. 9As shown, when the energy storage is connected to node 11 and the charging power reaches 10MW, the maximum effective value of the closing-loop impact current drops to 512.74A, which is less than the maximum control current of branch 25-29 of 521A, meeting the intraday safety verification of the closing-loop current, and the closing-loop operation can be performed at this time.

[0165] The beneficial effects of the present invention are as follows: by constructing a two-stage optimization control model of the day-ahead and day-intraday of the load transfer of the active distribution network under multiple energy forms, a method for calculating the short-circuit current of the active distribution network loop that is adapted to the new power system is proposed, which effectively simulates the size of the impact current of the active distribution network's live load transfer loop, reduces the risk of loop transfer failure, improves the reliability, flexibility and economy of the active distribution network's operation, reduces the risk of loop transfer failure that may exist in the future, and improves the scientific leanness of power grid planning and the active operation control capabilities.

[0166] The above description is a preferred embodiment of the present invention, which is only used to illustrate the technical solution of the present invention and is not used to limit the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principle and scope of the present invention are covered by the protection scope of the claims of the present invention.

Claims

1. A two-stage optimization control method for active distribution network load transfer before and during the day, characterized in that: The following steps are involved: S1. Based on the DC power flow constraint and aiming at the lowest system day-ahead operation cost, a day-ahead optimization operation model for active distribution network day-ahead load transfer in all periods is constructed; S2. Based on the day-ahead optimization operation model, the day-ahead steady-state loop-closing impulse current amplitude and the maximum effective value of the loop-closing impulse current of the active distribution network with live load transferred to the electric gas branch are calculated, and the time period when the maximum effective value of the loop-closing impulse current can meet the safety current of the electric branch is selected as the intra-day preparatory loop-closing period; S3. Considering the scheduling of flexible resources such as energy storage and based on DC power flow constraints, the daily optimization control model of active distribution network live load transfer is constructed with the goal of minimizing the system's daily operating cost; S4. Based on the intra-day optimization control model, the maximum effective value of the intra-day closed-loop impulse current of the active distribution network with live load transferred to the electric gas branch is calculated; S5. If the maximum effective value of the intra-day closing-loop impulse current calculated by S4 meets the safety current requirement of the electrical branch, the active distribution network live load transfer operation is performed during the intra-day preparation closing-loop period; if it does not meet the requirement, the real-time charging and discharging power of the energy storage is adjusted by stepping, and then the process returns to step S4 to recalculate the intra-day closing-loop impulse current until it is met.

2. The method according to claim 1, characterized in that: The day-ahead optimization operation model includes a first objective function with the lowest day-ahead operation cost of the system and a corresponding first constraint condition; The first objective function: In the formula, is the electricity price of node a in period t in the previous day, is the electric power of the generator set at node a during period t in the day-ahead phase; The first constraint condition includes the power system equivalent DC operation constraint and the new energy output forecast constraint in the day-ahead stage. The power system equivalent DC operation constraint in the day-ahead stage includes the power node power conservation constraint, line transmission capacity constraint, generator output upper and lower limit constraint, generator ramp upper and lower limit constraint, and system phase angle operation constraint: In the formula, is the power generation power of photovoltaic unit m in the period t before the day, is the power generation of wind turbine n in period t the day before, is the phase angle of node i in period t before the day, is the phase angle of node j in period t a day ago, is the output of the mth generator set in the t-day period, is the output of the mth generator set in the period t-1 the day before, is the actual power consumption of load b during period t the day before, b ij is the susceptance parameter of branch ij, is the phase angle of node 1 of the power system at time t a day ago. Node 1 is set as a balanced node with a phase angle of 0. is the maximum transmission power corresponding to the distribution line ij, are the maximum limits of landslide and climbing power corresponding to generator set m respectively; The current new energy output forecast constraints include wind power and photovoltaic output forecast constraints. The wind power output forecast constraints are as follows: Where α is the correlation coefficient of surface roughness, v ref (t) is the wind speed measured by the fan, v is the theoretical wind speed, H ref H is the installation height of the wind measuring device DA is the actual height of the fan hub, v ci is the wind turbine cut-in wind speed, v cr is the rated wind speed of the fan, v co is the maximum allowable wind speed, P r (v) is the wind turbine fitting output power curve, P r is the rated output power of the fan; The photovoltaic output forecast constraint is as follows: In the formula, f pv is the rated energy conversion power of the photovoltaic array, P rate is the rated power generation of the photovoltaic array, A is the actual photovoltaic irradiance of the photovoltaic array; A s is the photovoltaic rated irradiance; α p is the power temperature coefficient; T STC is the test temperature of photovoltaic modules under standard test conditions, T is the actual temperature, is the real-time power of the photovoltaic power station, η4 is the conversion efficiency of solar energy to direct current, η inv is the inverter AC-DC conversion efficiency, A pv is the total area of ​​PV panels, Total solar radiation, is the abandoned light power of the PV power station in period t, is the rated power of the PV power station.

3. The method according to claim 1, characterized in that: Based on the day-ahead optimization operation model, the day-ahead steady-state loop-closing impulse current amplitude and the maximum effective value of the loop-closing impulse current of the day-ahead active distribution network live load transferred to the power gas branch are calculated as follows: In the S1 day-ahead optimization operation model, the new energy output, load forecast and distribution network topology parameters for the 24 hours the day before are input, and the day-ahead steady-state loop impact current amplitude of the active distribution network's live load transferred to the gas branch is calculated. Based on the Thevenin equivalent circuit, the maximum value of the closed-loop impulse current is derived, and the formula is shown as follows: The Thevenin equivalent potential is are the amplitude and phase angle of the steady-state voltage difference at the closed loop obtained in the day-ahead stage, and the Thevenin equivalent impedance is expressed as Z eq =R eq +jωL eq ; Solving formula (12) can obtain the expression of the day-ahead loop impact current: From the above formula, we can know that the closed-loop impulse current consists of a periodic component and a non-periodic component. The maximum value of the closing loop impact current before the day is: In the formula, is the impact coefficient, is the amplitude of the steady-state closed-loop impulse current the day before; Furthermore, by integrating the first cycle of formula (13), the maximum effective value of the closed-loop impulse current within a day is obtained as follows: In the formula, It is the maximum effective value of the closed-loop impulse current within a day.

4. The method according to claim 1, characterized in that: The intraday optimization control model includes a second objective function with the lowest intraday operating cost of the system and a corresponding second constraint condition; The second objective function: In the formula, is the electricity price of node a in the next period of the day, is the power of the generator set at node a in the next period of the day, π ES,RT is the equivalent charging and discharging price of the energy storage system in the next period of the day, p ES,RT is the charging and discharging power of the energy storage system in the next period of the day, N E It is an energy storage accessible node. is the charge and discharge energy of the kth energy storage at node i at time t; The second constraint condition includes the equivalent DC operation constraint of the power system in the intraday stage and the optimal operation constraint of the energy storage system; the equivalent DC operation constraint of the power system in the intraday stage includes the power conservation constraint of the power node, the line transmission capacity constraint, the upper and lower limit constraints of the output of the generator set, the upper and lower limit constraints of the ramping of the generator set, and the phase angle operation constraint of the system: In the formula, is the power generation power of photovoltaic unit m during period t in a day, is the power generation of wind turbine n during period t in a day, is the phase angle of node i in period t within the day, is the phase angle of node j in period t within the day, is the output of the mth generator set during period t in the day, is the output of the mth generator set in the t-1 period of the day, is the actual power consumption of load b during period t in the day, b ij is the susceptance parameter of branch ij, is the phase angle of power system node i at time t within the day, node 1 is a balanced node, and the phase angle is 0, is the maximum transmission power corresponding to the distribution line ij, are the maximum limits of landslide and climbing power corresponding to generator set m respectively; Considering the scheduling of flexible resources such as energy storage, the optimal operation constraints of the energy storage system are as follows: Where η ch , η dis SOC is the energy storage charging and discharging efficiency; k，t is the remaining energy of the kth energy storage at time t, SOC k，max and SOC k，min Corresponding to the maximum and minimum capacity of MES, SOC k，0 is the initial electrical energy.

5. The method according to claim 1, characterized in that: Step S4 specifically includes the following steps: The daily optimization control model inputs the parameters such as the new energy output of the active distribution network within one hour, load forecast, real-time charging and discharging power of energy storage, and distribution network topology, and calculates the daily steady-state closed-loop impact current amplitude of the active distribution network's live load transferred to the electricity and gas branch. The maximum value of the closed-loop impact current within a day is derived according to the following formula: The Thevenin equivalent potential is are the amplitude and phase angle of the steady-state voltage difference at the closed loop obtained during the intraday period, and the Thevenin equivalent impedance is expressed as Z eq =R eq +jωL eq , solving formula (24) can obtain the expression of closed-loop impulse current: From the above formula, we can know that the closed-loop impulse current consists of a periodic component and a non-periodic component. The maximum instantaneous value of the intra-day closed-loop impact current is: In the formula, is the impact coefficient, is the daily steady-state closed-loop current amplitude; Furthermore, by integrating the first cycle of formula (25), the maximum effective value of the closed-loop impulse current within a day is obtained as follows: In the formula, It is the maximum effective value of the closed-loop impulse current within a day.

6. The method according to claim 1, characterized in that: The real-time charging and discharging power of energy storage is regulated by stepping, specifically: The charging and discharging power step of the energy storage system is set to 0.1 times the charging and discharging power, as shown in the following formula: In the formula, is the unit step length of charge and discharge power, Maximum charge and discharge power.

7. A two-stage optimization control device for active distribution network load transfer before and during the day, characterized in that: include: A day-ahead optimization operation model construction module, wherein the day-ahead optimization operation model is used to construct a day-ahead optimization operation model for the active distribution network for the entire period of day-ahead load transfer based on DC power flow constraints and with the goal of minimizing the day-ahead operation cost of the system; A model for determining a preparatory closing period, wherein the model is used to calculate the day-ahead steady-state closing impulse current amplitude and the maximum effective value of the closing impulse current of the active distribution network with live load transferred to the electric gas branch based on the day-ahead optimization operation model, and select the time period when the maximum effective value of the closing impulse current can meet the safety current of the electric branch as the intra-day preparatory closing period; An intraday optimization control model construction module, wherein the intraday optimization control model is used to consider the scheduling of flexible resources such as energy storage and to construct an intraday optimization control model for active distribution network live load transfer day based on DC power flow constraints with the goal of minimizing the system's intraday operating cost; A closed-loop impulse current maximum effective value calculation module, which is used to calculate the maximum effective value of the closed-loop impulse current within a day when the live load of the active distribution network is transferred to the gas branch based on the intra-day optimization control model; The transfer control module is used to perform the active distribution network live load transfer operation during the intra-day preparatory closing period when the calculated maximum effective value of the intra-day closing impact current meets the electrical branch circuit safety current requirement.

8. A computer device comprising a processor and a memory, characterized in that: The memory stores a computer simulation program; the processor is capable of implementing the optimization control step described in any one of claims 1 to 6 when executing the computer simulation program.

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