Flexible phase-shifting transformer control method and device based on load prediction

Abstract

The application provides a flexible phase-shifting transformer control method and device based on load prediction, and belongs to the field of transformer control. The method comprises the following steps: inputting historical load data into a day-ahead load prediction optimization model constructed in advance, and outputting day-ahead load prediction data; the model is established with the minimum power flow fluctuation as the target, and the line power flow balance, the number of phase shifter gear adjustment and the thermal stability limit power as the constraint conditions; the day-ahead load prediction data is solved based on a mixed integer optimization algorithm, the day-ahead prediction operation curve of the phase shifter gear is obtained, and the target gear and the adjusted phase angle difference are determined according to the phase angle adjustment corresponding table and the curve; wherein the phase angle adjustment corresponding table is constructed according to the gear of the tap switch and the phase-shifting angle; the tap switch is adjusted according to the target gear, and the voltage source type converter is controlled to act according to the phase angle difference. The application can ensure that the control stability of the flexible phase-shifting transformer is improved based on the day-ahead load prediction data, and the line utilization rate is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformer control, and particularly relates to a flexible phase-shifting transformer control method and device based on load prediction. BACKGROUND

[0002] With the development of smart grid and the continuous improvement of voltage level of power system, high-voltage alternating current transmission network is becoming more and more complex, forming a large number of parallel transmission channels, which leads to some problems such as uneven power flow distribution, low utilization rate, light load or overload of power flow, etc. Therefore, it is of great significance to use effective power flow control means to realize power flow balance, improve power quality and increase line transmission capacity.

[0003] A phase-shifting transformer changes the voltage amplitude and phase angle of the access point by inserting a transverse voltage or a longitudinal voltage in the transmission line, thereby controlling and changing the active power flow of the line. The traditional phase-shifting transformer (PST) has the outstanding advantages of low cost and wide-range regulation, but it is difficult to cope with the rapid power flow changes of modern power networks due to the long response time of mechanical regulation and the disadvantages of inflexible discrete regulation.

[0004] The flexible phase-shifting transformer combines a three-phase two-level bridge voltage source converter (VSC) and can efficiently integrate the advantages of traditional electromagnetic mechanical devices and power electronic devices. On the one hand, by means of the body regulation function of the phase shifter, a wide-range non-continuous regulation is realized through passive electromagnetic devices, while maintaining the characteristics of low cost and high reliability. On the other hand, precise and fast continuous regulation is realized by using a voltage source converter. This hybrid power flow control equipment exhibits significant advantages in overall insulation, volume and cost. However, there is currently a lack of efficient control means to effectively and accurately regulate power flow in the system. SUMMARY

[0005] Embodiments of the present application provide a flexible phase-shifting transformer control method and device based on load prediction to solve the problem of how to effectively and accurately regulate power flow in the system.

[0006] In a first aspect, embodiments of the present application provide a flexible phase-shifting transformer control method based on load prediction. The flexible phase-shifting transformer includes a series transformer, an excitation transformer and a voltage source converter. The secondary winding of the excitation transformer includes a tap changer. The method comprises:

[0007] The historical load data is acquired and input into a pre-built day-ahead load prediction optimization model to output day-ahead load prediction data; wherein the day-ahead load prediction optimization model is built with the objective of minimizing power flow fluctuation and with the constraint conditions of line power flow balance, phase shifter gear adjustment times and thermal stability limit power;

[0008] The day-ahead load prediction data is solved based on a mixed integer optimization algorithm to obtain a day-ahead predicted operation curve of the phase shifter gear, and the target gear and adjusted phase angle difference are determined according to a phase angle adjustment corresponding table and the day-ahead predicted operation curve; wherein the phase angle adjustment corresponding table is built according to the gear of the tap switch and the phase shift angle;

[0009] The tap switch is adjusted according to the target gear, and the voltage source type converter is controlled to act according to the phase angle difference.

[0010] In a possible implementation, the day-ahead load prediction optimization model is:

[0011]

[0012] wherein P is the total power flow change of the system, P pre is the active power flow of the current system; P ref is the load reference value; i is any node in the system.

[0013] In a possible implementation, the constraint condition corresponding to the line power flow balance is:

[0014] Q i,G -Q i,L -U j (G ij sinθ ij -B ij cosθ ij )=0

[0015] wherein i is any node in the system, j is a certain node adjacent to the i node; Q G is the node power generation reactive power, Q L is the node load reactive power; G and B are respectively the real part and the imaginary part of the line admittance; and θ is the voltage phase angle difference between nodes.

[0016] In a possible implementation, the constraint condition corresponding to the line power flow balance is:

[0017]

[0018] wherein T is a time interval, D is the gear of the tap switch, from -n to n gears, and t is the time step taken.

[0019] In one possible implementation, the constraint condition corresponding to the line power flow balance is:

[0020] I 2 R(T c )+Q s =Q c +Q r

[0021]

[0022] Where I represents the current carrying capacity of the specified conductor under the allowable temperature conditions, and R(T) c ) is the conductor at temperature T c AC resistance at time; Q s The conductor absorbs heat from sunlight; Q c For convective heat dissipation of the conductor; Q r Heat dissipation through radiation from the conductor; U N The rated voltage (kV) of the line; I max For line current limits; The power factor.

[0023] In one possible implementation, the phase angle adjustment correspondence table includes: gear position, simulated no-load phase angle value, calculated no-load phase angle value, and load phase shift angle.

[0024] In one possible implementation, determining the target gear and the adjusted phase angle difference based on the phase angle adjustment correspondence table and the day-ahead predicted operating curve includes:

[0025] Obtain the voltage phasors at both ends of the line, and determine the required active power reference value of the system based on the day-ahead predicted operating curve;

[0026] Based on the active power reference value and the voltage phasors at the beginning and end of the line, calculate the required phase shift angle reference value and voltage amplitude reference value;

[0027] The target gear is selected based on the principle of prioritizing the distance between the phase shift angle reference value and the no-load phase shift angle.

[0028] In one possible implementation, the formula for calculating the phase shift angle reference value is:

[0029]

[0030] Where, θ ref P is the phase shift angle reference value. ref The active power reference value required by the system; U L U is the voltage phasor at the end of the line; S R is the voltage phasor at the beginning of the line; L This represents the line load.

[0031] In a possible implementation, the voltage adjusted according to the target gear is:

[0032]

[0033] wherein U dN is the voltage adjusted according to the target gear; U pal is a voltage amplitude reference value; δ N is a phase shift angle corresponding to the target gear.

[0034] In a second aspect, an embodiment of the present application provides a flexible phase-shifting transformer control device based on load prediction, the flexible phase-shifting transformer comprising a series transformer, an excitation transformer and a voltage source converter; the secondary winding of the excitation transformer comprising a tap changer; the device comprising:

[0035] an acquisition module configured to acquire historical load data;

[0036] a prediction module configured to input the historical load data into a day-ahead load prediction optimization model built in advance, and output day-ahead load prediction data; wherein the day-ahead load prediction optimization model is built with the objective of minimizing power flow fluctuation, and with line power flow balance, phase shifter gear adjustment frequency and thermal stability limit power as constraint conditions;

[0037] a calculation module configured to solve the day-ahead load prediction data based on a mixed integer optimization algorithm, obtain a day-ahead prediction operation curve of the phase shifter gear, and determine a target gear and an adjusted phase angle difference according to a phase angle adjustment corresponding table and the day-ahead prediction operation curve; wherein the phase angle adjustment corresponding table is built according to the gear of the tap changer and the phase shift angle;

[0038] a control module configured to adjust the tap changer according to the target gear, and control the voltage source converter to act according to the phase angle difference.

[0039] The embodiment of the present application provides a flexible phase-shifting transformer control method and device based on load prediction, through historical load data input and a day-ahead load prediction optimization model constructed in advance, day-ahead load prediction data is obtained, the day-ahead load prediction optimization model is established with the minimum power flow fluctuation as the target, and the line power flow balance, the phase shifter gear adjustment frequency and the thermal stability limit power are taken as the constraint conditions, so that the control stability of the flexible phase-shifting transformer is improved based on the day-ahead load prediction data, and the line utilization rate is improved. The day-ahead load prediction data is solved based on a mixed integer optimization algorithm, a day-ahead prediction operation curve of the phase shifter gear is obtained, the target gear and the adjusted phase angle difference are determined according to the corresponding table of the phase angle adjustment and the day-ahead prediction operation curve, the tap switch is adjusted according to the target gear, and the voltage source type converter is controlled to act according to the phase angle difference, so as to make up for the deficiency of PST discrete adjustment, and the continuous adjustment of VSC is also achieved. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0041] Figure 1 is a topological graph of a flexible phase-shifting transformer provided by an embodiment of the present application;

[0042] Figure 2 is an internal equivalent circuit diagram of a flexible phase-shifting transformer provided by an embodiment of the present application;

[0043] Figure 3 is an A-phase equivalent circuit provided by an embodiment of the present application;

[0044] Figure 4 is a schematic diagram of transformer phase-shifting angle and tap gear provided by an embodiment of the present application;

[0045] Figure 5 is a schematic diagram of overall tap gear adjustment area provided by an embodiment of the present application;

[0046] Figure 6 is a flowchart of a flexible phase-shifting transformer control method based on load prediction provided by an embodiment of the present application;

[0047] Figure 7 is a day-ahead prediction operation curve diagram of a phase shifter gear provided by an embodiment of the present application;

[0048] Figure 8 is a schematic diagram of overall tap gear adjustment area provided by another embodiment of the present application;

[0049] Figure 9 is a schematic diagram of the whole regulation region of tap-off gear provided by another embodiment of the present application;

[0050] Figure 10 is a schematic diagram of VSC structure provided by an embodiment of the present application;

[0051] Figure 11 is a schematic diagram of target gear and VSC control process provided by an embodiment of the present application;

[0052] Figure 12 is a schematic diagram of the structure of the flexible phase-shifting transformer control device based on load prediction provided by an embodiment of the present application. DETAILED DESCRIPTION

[0053] In the following description, for the purpose of explanation and not limitation, specific details are set forth, such as particular system configurations, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

[0054] Before implementing the flexible phase-shifting transformer control method based on load prediction provided by the present application, preparation work needs to be done.

[0055] First, the structure of the flexible phase-shifting transformer is analyzed, which is generally composed of a series transformer, an exciting transformer, and a voltage source converter (VSC), as shown in Figure 1 The primary side of the series transformer (ST) is connected in series in the line, and the secondary side is connected in delta. The primary side and the secondary side of the exciting transformer (ET) are both connected in Yn. The primary side winding of the series transformer is divided into two sections, and the middle terminal is connected to the primary side of the exciting transformer. The first and last terminals of each phase winding of the secondary side are connected to the secondary side windings of the other two phases of the exciting transformer. The ET secondary side winding is connected to the voltage source converter through a tap-off switch to control the turns ratio, and the voltage source converter is connected to the end to control the phase shift and change the phase shift angle

[0056] If the impedance of each winding inside the phase shifter and the internal impedance of the VSC are considered, and the A phase is analyzed as an example, the internal equivalent circuit of the flexible phase-shifting transformer can be as shown in Figure 2 The tap-off switch is used for voltage and phase discrete regulation, and the VSC is used for continuous regulation. In order to facilitate analysis, the effect of the VSC is temporarily not considered, and the end of the secondary side of the exciting transformer is grounded to obtain the A phase equivalent circuit simplified diagram as shown in Figure 3 .

[0057] Next, vector analysis and vector diagram are carried out.

[0058] ST primary winding is divided into two parts, so the leakage impedance of the power supply side and the load side is equal, that is, Z SA ' = Z SA " = Z SA / 2. The following formula can be obtained:

[0059]

[0060] The voltage and current relationship of the ET primary and secondary sides can be expressed as:

[0061]

[0062] From the vector diagram, the orthogonal voltage generated at the ST secondary side can also be represented by the secondary voltage of the ET:

[0063]

[0064]

[0065] Substitute (4) and (5) into (1) to eliminate the parameters of the series-to-secondary winding, and the following can be obtained:

[0066]

[0067] Combined with the expression of U Ea , the voltage relationship between the input and output of the phase-shifting transformer can be obtained:

[0068]

[0069] The no-load phase-shifting angle α is:

[0070]

[0071] According to this formula, the only influencing factor of the no-load phase-shifting angle is the tap position D of the tap switch, and when D changes between 0 and 1, the angle is directly proportional to the change.

[0072] Taking a 230kV phase-shifting transformer as an example, the phase-shifting capability is simulated and analyzed under load and no-load conditions, and the corresponding relationship between the tap position and the phase-shifting angle can be obtained as shown in Table 1, that is, the phase angle adjustment corresponding table.

[0073] Table 1 Phase-shifting angle under different tap positions

[0074]

[0075]

[0076] It can be seen that the phase shift angle changes little under different loads, and has an absolute relationship with the tap switch position. That is, the tap position can be determined according to the required angle, and the slight deviation is further supplemented by the VSC.

[0077] According to the above steps, the phase shift angle of a certain type of transformer can be corresponded to the tap gear position, as shown in Figure 4 .

[0078] Next, taking the input end voltage phase of the transformer as the positive direction of the Y axis, and the output end voltage phase as the possible lag or lead, connecting the two extreme limit voltages of the lag and the lead, and equally dividing them according to the angle, the voltage value required to be injected into the series transformer by the excitation transformer under different angles can be obtained, and a series of intersection points are formed on the horizontal line. The overall adjustment range of the tap gear position is shown in Figure 5 .

[0079] The adjustment effect of the gear position on the voltage phase is a fixed point discrete adjustment in the same or opposite direction in a single dimension, while the corresponding phase of the VSC is continuously adjustable in the four quadrants, that is, a circle of the same size is made at each intersection point, completing the full-angle coverage in the entire region. If the end point of the VSC continues to adjust after the PST, the boundary position of the adjustment region can be represented as:

[0080]

[0081] To make the purpose, technical scheme and advantages of the present application clearer, specific embodiments will be described below with reference to the drawings.

[0082] Figure 6 The implementation flowchart of the flexible phase-shifting transformer control method based on load prediction provided for the embodiments of the present application is described in detail as follows:

[0083] In step 601, historical load data is obtained, and the historical load data is input into a pre-constructed day-ahead load prediction optimization model to output day-ahead load prediction data. The day-ahead load prediction optimization model is established with the minimization of power flow fluctuation as the target, and the line power flow balance, the number of tap position adjustments of the phase shifter, and the thermal stability limit power as the constraint conditions.

[0084] In step 602, the day-ahead load prediction data is solved based on a mixed integer optimization algorithm to obtain a day-ahead prediction operation curve of the tap position of the phase shifter, and the target gear position and the adjusted phase angle difference are determined according to a phase angle adjustment corresponding table and the day-ahead prediction operation curve. The phase angle adjustment corresponding table is constructed according to the gear position of the tap switch and the phase shift angle.

[0085] The adjusted phase angle difference is determined to achieve that after the tap position is determined according to the required angle, the slight phase angle deviation is further supplemented by the VSC adjustment.

[0086] Step S603, adjust the tap changer according to the target gear, and control the VSC action according to the phase angle difference.

[0087] In a possible implementation, the day-ahead load forecasting optimization model is:

[0088]

[0089] wherein P is the total power flow change of the system, P pre is the active power flow of the current system; P ref is the load reference value; and i is any node in the system.

[0090] In a possible implementation, the constraint condition corresponding to the line power flow balance is:

[0091] Q i,G -Q i,L -U j (G ij sinθ ij -B ij cosθ ij )=0 (11)

[0092] wherein i is any node in the system, j is a node adjacent to the i node; Q G is the node power generation reactive power, Q L is the node load reactive power; G and B are respectively the real part and the imaginary part of the line admittance; and θ is the voltage phase angle difference between nodes.

[0093] In a possible implementation, the constraint condition corresponding to the line power flow balance is:

[0094]

[0095] wherein T is a time interval, D is the tap changer gear, from -n to n gears, and t is the time step taken.

[0096] In a possible implementation, the constraint condition corresponding to the line power flow balance is:

[0097]

[0098] wherein I is the current-carrying capacity of the specified conductor under the allowable temperature condition, R(T c ) is the alternating current resistance of the conductor at temperature T c ; Q s is the heat absorption of the conductor under sunlight; Q c is the convection heat dissipation of the conductor; Q r is the radiation heat dissipation of the conductor; and U NThe rated voltage (kV) of the line; I max Line current limit; The power factor.

[0099] like Figure 7 The diagram shows the day-ahead predicted operating curve of the phase shifter. Based on the day-ahead predicted operating curve, the real-time target optimal load of the system can be obtained, and the phase shifter can be controlled with this target optimal load.

[0100] In one possible implementation, the phase angle adjustment correspondence table includes: gear position, simulated no-load phase angle value, calculated no-load phase angle value, and load phase shift angle.

[0101] Specifically, the phase angle adjustment correspondence table is shown in Table 1.

[0102] In one possible implementation, the target gear and the adjusted phase angle difference are determined based on a phase angle adjustment correspondence table and a day-ahead predicted operating curve, including:

[0103] Obtain the voltage phasors at both ends of the line, and determine the required active power reference value of the system based on the day-ahead predicted operating curve;

[0104] Based on the active power reference value and the voltage phasors at the beginning and end of the line, calculate the required phase shift angle reference value and voltage amplitude reference value;

[0105] Select the target gear based on the principle of prioritizing the distance between the phase shift angle reference value and the no-load phase shift angle.

[0106] In one possible implementation, the formula for calculating the phase shift angle reference value is:

[0107]

[0108] Where, θ ref P is the phase shift angle reference value. ref The active power reference value required by the system; U L U is the voltage phasor at the end of the line; S R is the voltage phasor at the beginning of the line; L This represents the line load.

[0109] In the specific implementation process, with Figure 5 Using the overall adjustment area of ​​the tap position shown as a reference, and taking the angle as the primary criterion, the point closest to the target tap position of the excitation transformer tap switch is selected on a horizontal straight line based on the target adjustment angle and polarity.

[0110] In one possible implementation, the voltage adjusted according to the target gear is:

[0111]

[0112] Among them, U dN The voltage after adjustment according to the target gear; U pal This is the reference value for voltage amplitude; δ N The phase shift angle corresponding to the target gear.

[0113] Specifically, such as Figure 8 As shown, when the current voltage reference value of the phase shifter with ±4 adjustment is at the dashed line, the tap changer should be adjusted to +3.

[0114] The target angle should be within the circle centered at that point. The target angle phasor intersects the circle at two points; this represents precise control. The point with the smallest voltage amplitude deviation between the two points is selected for voltage injection into the VSC, controlling its internal switching. Figure 9 For example, the intersection point above is obviously closer to the standard voltage amplitude, so the voltage at that point should guide the VSC operation.

[0115] VSC consists of four cascaded H-bridges of three phases, such as Figure 10 As shown, the switching of each IGBT controls the rise and fall of the voltage waveform. IGBT on is defined as 1, and off as 0. There are 48 switches in total, representing a 0-1 integer programming problem. An implicit enumeration method is used to check all possible variable combinations before reaching the optimal solution, thereby determining the on / off state of each switch. The angle is calculated; if there is an error, the above process of adjusting the tap changer to the target position and controlling the VSC action is repeated according to the magnitude of the error, or the VSC action is controlled. Specifically... Figure 11 As shown.

[0116] In this embodiment, day-ahead load forecast data is obtained by inputting historical load data and using a pre-built day-ahead load forecast optimization model. The day-ahead load forecast optimization model is established with the goal of minimizing power flow fluctuations and is constrained by line power flow balance, the number of phase shifter tap adjustments, and thermal stability limit power. This ensures that the control stability of the flexible phase-shifting transformer is improved based on the day-ahead load forecast data, thereby increasing line utilization. The day-ahead load forecast data is solved using a mixed integer optimization algorithm to obtain the day-ahead forecast operating curve of the phase shifter tap. The target tap and the adjusted phase angle difference are determined according to the phase angle adjustment correspondence table and the day-ahead forecast operating curve. The tap changer is adjusted according to the target tap, and the voltage source converter is controlled according to the phase angle difference. This compensates for the shortcomings of PST discrete adjustment and also has the continuous adjustment of VSC.

[0117] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0118] The following is an embodiment of the device of the present application, for details not described in detail, can refer to the corresponding method embodiment described above.

[0119] Figure 12 The structure diagram of the flexible phase-shifting transformer control device based on load prediction provided by the embodiment of the present application is shown, only the part related to the embodiment of the present application is shown for the convenience of description, and the details are described as follows:

[0120] As Figure 12 shown, the flexible phase-shifting transformer control device 12 based on load prediction comprises:

[0121] The acquisition module 1201 is configured to acquire historical load data.

[0122] The prediction module 1202 is configured to input the historical load data into a pre-constructed day-ahead load prediction optimization model, and output day-ahead load prediction data; wherein the day-ahead load prediction optimization model is established with the minimum power flow fluctuation as the target, and with the line power flow balance, the phase shifter gear adjustment frequency and the thermal stability limit power as the constraint conditions.

[0123] The calculation module 1203 is configured to solve the day-ahead load prediction data based on a mixed integer optimization algorithm, obtain a day-ahead prediction operation curve of the phase shifter gear, and determine the target gear and the adjusted phase angle difference according to the phase angle adjustment corresponding table and the day-ahead prediction operation curve; wherein the phase angle adjustment corresponding table is constructed according to the gear of the tap switch and the phase-shifting angle.

[0124] The control module 1204 is configured to adjust the tap switch according to the target gear, and control the voltage source type converter to act according to the phase angle difference.

[0125] In a possible implementation, the day-ahead load prediction optimization model is:

[0126]

[0127] Wherein, P is the total power flow change of the system, P pre is the active power flow of the current system; P ref is the load reference value; i is any node in the system.

[0128] In a possible implementation, the constraint condition corresponding to the line power flow balance is:

[0129] Q i,G -Q i,L -U j (G ij sinθ ij -B ij cosθ ij )=0 (17)

[0130] wherein, i is any node in the system, j is a node adjacent to i; Q G is the active power of the node; Q L is the reactive power of the node; G and B are the real part and imaginary part of the line admittance respectively; and θ is the phase angle difference between the nodes.

[0131] In a possible implementation, the constraint condition corresponding to the line power flow balance is:

[0132]

[0133] wherein, T is a time interval, D is the tap position of the tap switch, from -n to n, and t is the time step taken.

[0134] In a possible implementation, the constraint condition corresponding to the line power flow balance is:

[0135]

[0136] wherein, I is the current-carrying capacity of the specified conductor under the allowable temperature condition, R(T c ) is the alternating current resistance of the conductor at temperature T c ; Q s is the heat absorption of the conductor under sunlight; Q c is the convection heat dissipation of the conductor; Q r is the radiation heat dissipation of the conductor; U N is the rated voltage (kV) of the line; I max is the current limit of the line; is the power factor.

[0137] In a possible implementation, the phase angle adjustment corresponding table includes: tap position, no-load phase angle simulation value, no-load phase angle calculation value, and load phase shift angle.

[0138] In a possible implementation, the calculation module 1203 is specifically configured to:

[0139] obtain the voltage phasor at the two ends of the line, and determine the active reference value required by the system according to the day-ahead prediction operation curve;

[0140] calculate the required phase shift angle reference value and voltage amplitude reference value according to the active reference value and the voltage phasor at the two ends of the line;

[0141] select the target tap position according to the distance priority principle between the phase shift angle reference value and the no-load phase shift angle.

[0142] In a possible implementation, the phase shift angle reference value calculation formula is:

[0143]

[0144] wherein θ ref is the phase shift angle reference value; P ref is the active power reference value required by the system; U L is the voltage phasor at the end of the line; U S is the voltage phasor at the beginning of the line; R L is the load of the line.

[0145] In a possible implementation, the voltage adjusted according to the target gear is:

[0146]

[0147] wherein U dN is the voltage adjusted according to the target gear; U pal is the voltage amplitude reference value; δ N is the phase shift angle corresponding to the target gear.

[0148] In the embodiment, the day-ahead load prediction data is obtained through historical load data input and a day-ahead load prediction optimization model built in advance. The day-ahead load prediction optimization model is established with the minimization of power flow fluctuation as the target, and with the line power flow balance, the number of phase shifter gear adjustments and the thermal stability limit power as the constraint conditions, to ensure that the control stability of the flexible phase-shifting transformer is improved based on the day-ahead load prediction data, and the line utilization rate is improved. The day-ahead load prediction data is solved based on a mixed integer optimization algorithm, to obtain a day-ahead prediction operation curve of the phase shifter gear, and the target gear and the adjusted phase angle difference are determined according to the phase angle adjustment corresponding table and the day-ahead prediction operation curve. The tap changer is adjusted according to the target gear, and the voltage source converter is controlled to act according to the phase angle difference, to make up for the deficiency of PST discrete adjustment, and to have the continuous adjustment of VSC.

[0149] In the above embodiments, the description of each embodiment has its own focus, and the parts not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0150] Those of ordinary skill in the art can realize that the templates, units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software mode depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0151] The modules / units, if realized in the form of software function units and sold or used as independent products, can be stored in a computer readable storage medium. Based on such understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the computer program is executed by a processor, the steps of each of the above-mentioned flexible phase-shifting transformer control methods based on load prediction can be realized. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms, etc. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0152] The above-mentioned embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A flexible phase-shifting transformer control method based on load prediction, the flexible phase-shifting transformer comprising a series transformer, an excitation transformer, and a voltage source converter; The excitation transformer secondary side winding comprises a tap changer; characterized in that The method comprises: obtaining historical load data, and inputting the historical load data into a day-ahead load prediction optimization model built in advance to output day-ahead load prediction data; wherein the day-ahead load prediction optimization model is established with the objective of minimizing power flow fluctuation, and with line power flow balance, phase shifter gear adjustment frequency and thermal stability limit power as constraint conditions; the day-ahead load prediction data is solved based on a mixed integer optimization algorithm to obtain a day-ahead prediction operation curve of the phase shifter gear, and target gear and adjusted phase angle difference are determined according to a phase angle adjustment corresponding table and the day-ahead prediction operation curve; wherein the phase angle adjustment corresponding table is built according to the gear of the tap changer and the phase shift angle; the tap changer is adjusted according to the target gear, and the voltage source type converter is controlled to act according to the phase angle difference; The phase angle adjustment corresponding table comprises: gear, no-load phase angle simulation value, no-load phase angle calculation value and load phase shift angle; The phase angle adjustment corresponding table comprises: gear, no-load phase angle simulation value, no-load phase angle calculation value and load phase shift angle; The phase angle adjustment corresponding table comprises: gear, no-load phase angle simulation value, no-load phase angle calculation value and load phase shift angle; The voltage phasor at the two ends of the line is obtained, and the active reference value required by the system is determined according to the day-ahead prediction operation curve; The required phase shift angle reference value and voltage amplitude reference value are calculated according to the active reference value and the voltage phasor at the two ends of the line; 2. The load prediction based flexible phase shifting transformer control method of claim 1, wherein, The target gear is selected according to the distance priority principle between the phase shift angle reference value and the no-load phase shift angle. wherein, is the total power flow change of the system, is the active power flow of the current system; is the load reference value; is any one node in the system.

3. The load prediction based flexible phase shifting transformer control method of claim 1, wherein, The day-ahead load prediction optimization model is: wherein, is the voltage at any node in the system, is a certain node adjacent to the node; is the generated reactive power at the node, is the load reactive power at the node; and are the real and imaginary parts of the line admittance, respectively; is the phase angle difference between the voltages at the nodes; is the voltage at the node .

4. The load prediction based flexible phase shifting transformer control method of claim 1, wherein, The constraint condition corresponding to the line power flow balance is: wherein is a time interval, is a tap changer gear position, from to gear, is a taken time step.

5. The load prediction based flexible phase shifting transformer control method of claim 1, wherein, The constraint condition corresponding to the line power flow balance is: wherein, is the current-carrying capacity of the conductor under the specified temperature conditions, is the AC resistance of the conductor at temperature is the solar heat gain of the conductor; is the convective heat loss of the conductor; is the radiative heat loss of the conductor; is the rated voltage of the line; is the current limit of the line; is the power factor; is the active reference value required by the system.​ 6. The load prediction based flexible phase shifting transformer control method of claim 5, wherein, The constraint condition corresponding to the line power flow balance is: wherein, is a phase-shifted angle reference value; is a system required active reference value; is a voltage phasor at the end of the line; is a voltage phasor at the beginning of the line; is a line load.

7. The load prediction based flexible phase shifting transformer control method of claim 1, wherein, The phase shift angle reference value calculation formula is: wherein, is the voltage adjusted according to the target gear; is the voltage amplitude reference value; is the phase shift angle corresponding to the target gear.

8. A load prediction based flexible phase shifting transformer control apparatus, the flexible phase shifting transformer comprising a series transformer, an excitation transformer and a voltage source converter; The voltage after adjustment according to the target gear is: The excitation transformer secondary side winding comprises a tap changer; characterized in that The device comprises: An acquisition module is configured to acquire historical load data; A prediction module is configured to input the historical load data into a day-ahead load prediction optimization model built in advance to output day-ahead load prediction data; wherein the day-ahead load prediction optimization model is established with the objective of minimizing power flow fluctuation, and with line power flow balance, phase shifter gear adjustment frequency and thermal stability limit power as constraint conditions; A calculation module is configured to solve the day-ahead load prediction data based on a mixed integer optimization algorithm to obtain a day-ahead prediction operation curve of the phase shifter gear, and determine target gear and adjusted phase angle difference according to a phase angle adjustment corresponding table and the day-ahead prediction operation curve; wherein the phase angle adjustment corresponding table is built according to the gear of the tap changer and the phase shift angle; A control module is configured to adjust the tap changer according to the target gear, and control the voltage source type converter to act according to the phase angle difference; The phase angle adjustment corresponding table comprises: gear, no-load phase angle simulation value, no-load phase angle calculation value and load phase shift angle; The calculation module is specifically configured to: The voltage phasor at the two ends of the line is obtained, and the active reference value required by the system is determined according to the day-ahead prediction operation curve; According to the active reference value and voltage phasors at both ends of the line, a required phase-shifting angle reference value and a voltage amplitude reference value are calculated; According to a distance priority principle between the phase-shifting angle reference value and a no-load phase-shifting angle, a target gear is selected.

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