A Power System Flow Optimization Method Considering HPFC Control Mode

Abstract

The present invention discloses a power system flow optimization method taking into account the HPFC control mode, and belongs to the field of power system stability and control. The HPFC equivalent model adopted by the power system flow optimization method of the present invention takes into account the reactance of the series coupled transformer, which is closer to reality, and derives the flow calculation method of HPFC under different control modes; the system economy and safety indicators are used as the objective function of the optimization model, the generator output and voltage, the transformer adjustable ratio, and the control target of HPFC are used as the control variables of the optimization model, and the constraint conditions of the optimization model are determined from the two aspects of power system operation and HPFC internal constraints, so that the optimization model is more comprehensive and rigorous; the HPFC control mode used in the calculation is not only the commonly used fixed power control mode, but also considers three other control modes such as voltage regulation control mode, phase angle regulation control mode, and impedance compensation control mode at the same time, and the calculation result can provide a reference for the selection of HPFC control mode.

Description

Technical Field

[0001] The present invention relates to the field of power system stability and control, and in particular to a power system power flow optimization method taking into account a HPFC control mode. Background Art

[0002] Hybrid Power Flow Controller (HPFC) is a hybrid flexible AC Transmission System (FACTS) device that has emerged in recent years. It consists of a unified power flow controller (UPFC) and a "Sen" transformer (ST). As a type of flexible AC transmission device, it can achieve fast, frequent, continuous, comprehensive and flexible control of large-scale interconnected power grids without changing the network structure, significantly improving the stability level and dynamic performance of the power grid, and enhancing the transmission capacity and power flow controllability of the power grid. Compared with traditional FACTS devices such as UPFC, HPFC combines the advantages of UPFC and ST. It not only has the same regulation characteristics as UPFC, but also has greatly reduced cost within the same regulation range, and has strong practical application value.

[0003] At present, most of the research on power flow optimization of FACTS only considers the power flow performance under the constant power control mode. When a system failure occurs, the control mode of HPFC will have a significant impact on the safety and stability of the system. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention proposes a power system power flow optimization method taking the HPFC control mode into consideration.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for optimizing power system flow taking into account the HPFC control mode comprises the following steps:

[0007] S1: Input grid data and N-1 expected fault sets, initialize control variables, which include control target values ​​of different HPFC control modes, adjustable generator output, PV node voltage, and tap adjustable transformer ratio;

[0008] S2: Perform power flow calculation of HPFC in constant power control mode. If the calculation result does not meet the constraint conditions, all control parameters are regenerated; if the conditions are met, the values ​​of each objective function are calculated;

[0009] S3: Perform power flow calculation of HPFC in other control modes. If the calculation result does not meet the constraint conditions, regenerate the control parameters corresponding to the control mode; if the conditions are met, calculate the values ​​of each objective function;

[0010] S4: Calculate the total objective function, record the individual optimal objective function and the group optimal objective function and their corresponding control variables and HPFC control modes;

[0011] S5: If the number of iterations does not reach the set value, go to S6, otherwise go to S7;

[0012] S6: Update the parameters and speed of the control variables and go to S2;

[0013] S7: Output power flow optimization results and optimal control mode.

[0014] Optionally, in step S2, the constant power control mode of the HPFC refers to controlling the series side voltage source so that the active and reactive power flows of the series side line reach ideal values.

[0015] Additional nodes m and n are introduced on line ij, and the additional node m is located between UPFC and ST, and the additional node n is located between ST and line impedance.

[0016] The power flow of line nj can be expressed as:

[0017]

[0018] V n ∠θ n =V i ∠θ i +V H ∠θ H (2)

[0019] Among them, V k ,θ k (k=i,j,m) represents the voltage amplitude and phase angle of the corresponding node; g L , b L Indicates the series conductance and susceptance of the line; B c Represents the line parallel susceptance; V H ,θ H Indicates the voltage amplitude and phase angle on the HPFC series side.

[0020] The combined equations (1) and (2) can be used to solve the voltage amplitude of the series side of the HPFC in the constant power control mode: and phase angle

[0021] For HPFC access lines, there are:

[0022]

[0023] in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the constant power control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the switching position of ST; Respectively represent the current phasors flowing through the UPFC and ST series side; X se , X cr denote the series transformer coupling reactance of UPFC and ST respectively;

[0024] According to the calculation result of formula (3), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

[0025] Optionally, the other modes include: one or more of a voltage regulation control mode, a phase angle regulation control mode, and an impedance compensation control mode;

[0026] Among them, the voltage regulation control mode refers to controlling the voltage amplitude of the HPFC series side when the phase angle of the HPFC series side voltage is the same as that of the parallel bus voltage; the phase angle adjustment control mode refers to controlling the phase angle of the series side voltage when the HPFC series side voltage and the parallel bus voltage amplitude are kept the same; the impedance compensation control mode refers to controlling the voltage of the series side voltage source and the current flowing through to maintain a constant value to compensate for the impedance of the controlled line.

[0027] Optionally, when the voltage amplitude V at node n n =V ref When , we can get:

[0028]

[0029] According to formula (4), the series side voltage amplitude of HPFC in voltage regulation control mode can be obtained as and phase angle

[0030] For HPFC access lines, there are:

[0031]

[0032] in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position.

[0033] According to the calculation result of formula (5), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

[0034] Optionally, taking the voltage of node i as reference, V H ∠θ H Decomposed into horizontal component V Hp and the vertical component V Hq , when the voltage phase angle difference between node i and node n is θ ref When , we can get:

[0035]

[0036]

[0037] in, is the phase angle difference between the HPFC series side voltage and the node i voltage.

[0038] The combined equations (6) and (7) can be used to solve the series side voltage amplitude of the HPFC in the phase angle regulation control mode: and phase angle

[0039] For HPFC access lines, there are:

[0040]

[0041] in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position.

[0042] According to the calculation result of formula (8), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

[0043] Optionally, when the HPFC compensation impedance target value is Z ref hour:

[0044]

[0045] in, Indicates the line series current phasor;

[0046] According to formula (9), the series side voltage amplitude of HPFC in impedance compensation control mode can be obtained as and phase angle

[0047] For HPFC access lines, there are:

[0048]

[0049] in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position.

[0050] According to the calculation result of formula (10), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

[0051] A computer-readable storage medium stores computer instructions, which, when executed, can implement any of the above-mentioned power system flow optimization methods.

[0052] Beneficial effects of the present invention:

[0053] The HPFC equivalent model adopted takes into account the reactance of the series coupled transformer, which is closer to reality, and derives the power flow calculation method of HPFC under different control modes; the system economy and safety indicators are used as the objective function of the optimization model, and the generator output and voltage, transformer adjustable ratio, and HPFC control target are used as the control variables of the optimization model. The constraints of the optimization model are determined from the two aspects of power system operation and HPFC internal constraints. The optimization model is more comprehensive and rigorous; the HPFC control mode used in the calculation is not only the commonly used constant power control mode, but also considers three other control modes such as voltage regulation control mode, phase angle regulation control mode, and impedance compensation control mode. The calculation results can provide a reference for the selection of HPFC control mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The present invention will be further described below in conjunction with the accompanying drawings.

[0055] Figure 1 A specific flow chart of the method in a specific embodiment of the present invention;

[0056] Figure 2 It is an equivalent circuit diagram of HPFC in a specific embodiment of the present invention;

[0057] Figure 3 : is a voltage phasor diagram of different HPFC control modes in a specific embodiment of the present invention, wherein Figure 3 (a): Voltage regulation control mode; Figure 3 (b): Phase angle adjustment control mode; Figure 3(c): Impedance compensation control mode. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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.

[0059] The technical solution of the present invention is further introduced below in conjunction with specific implementation methods.

[0060] This specific embodiment discloses a method for optimizing power system flow taking into account the HPFC control mode. The optimization model in this method includes three aspects: control variables, objective functions and constraint conditions.

[0061] 1) Control variables

[0062] Generally speaking, the control variables of the power system are mainly: the active power P of the generator g ; Generator node voltage V g (i.e. PV node voltage); transformer ratio T with taps.

[0063] For HPFC, the control variables are the constant voltage value V on the parallel side. shu ; In the constant power control mode, the active and reactive power flow target values ​​P of the controlled line are ref , Q ref ; In the voltage regulation control mode, there is a voltage target value V ref ; In the phase angle adjustment control mode, there is a phase angle target value θ ref ; In impedance compensation control mode, there is an impedance target value R ref , X ref .

[0064] 2) Objective Function

[0065] The optimization of the HPFC system is mainly considered from the two aspects of economy and safety. The objective function for measuring economy is the generator cost and system network loss. The objective function for measuring safety is the line safety index, busbar safety index and generator safety index. The specific calculation method of each objective function is as follows:

[0066] a. Generator cost.

[0067] The calculation formula of generator cost is as follows:

[0068]

[0069] Where Ng is the total number of generators in the system, a m 、b m 、c m are the power generation cost coefficient of the mth generator, P gm is the active power input into the system by the mth generator.

[0070] b. System network loss.

[0071] The network loss of the system is mainly the active power loss caused by the power flow through the line, that is:

[0072]

[0073] Where Nl is the total number of branches in the system; G m represents the conductance on the mth branch; V mi ,θ mi 、V mj ,θ mj are the voltage amplitude and phase angle of the head and end nodes of the mth branch respectively.

[0074] c. Line safety indicators.

[0075] The ratio of the line flow to the line flow limit is defined as the line load rate M. m , in order to reflect the operating status of the line.

[0076]

[0077] Among them, S m is the apparent power flowing through branch m, S mmax is the apparent power limit of branch m.

[0078] The system line safety index can be obtained through the line load rate:

[0079]

[0080] Among them, D line It represents the electrical distance from the system line operating point Q to the line static safety limit value LM.

[0081] When the line is overloaded during the calculation process, a penalty value needs to be added to the line safety index.

[0082] d. Busbar safety indicators

[0083] The bus safety index is used to measure the degree of deviation between the bus voltage operating point and its reference operating point, namely:

[0084]

[0085] Where Nb is the total number of buses in the system; V mmax 、V mmin are the upper and lower limits of the voltage amplitude of bus m.

[0086] e. Generator safety indicators

[0087] In order to ensure the safe operation of the generator, there are corresponding restrictions on the active and reactive output of the generator during operation. The generator safety index can be obtained based on the output limit of the generator:

[0088]

[0089] Among them, P gmmax , P gmmin , Q gmmax , Q gmmin are the upper and lower limits of the active and reactive output of the mth generator respectively.

[0090] Based on the above content, a system optimization objective function is established by comprehensively considering economy and safety:

[0091]

[0092] Among them, f is the overall objective function, f1 and f2 are the system economic and safety indicators respectively, η is the proportionality coefficient, and λ is the weight coefficient reflecting the importance of the indicator.

[0093] 3) Constraints

[0094] During the optimization process, the constraints of the power system operation and the HPFC itself must be met to ensure the normal operation of the power grid and HPFC.

[0095] a. Power system operation constraints.

[0096] For the power system, under normal operation, the node power balance needs to be met, that is:

[0097]

[0098] Where Nb is the total number of system nodes; P gi , Q gi are the active and reactive power of the generator respectively; P di , Q di are respectively the active and reactive loads of the load node; G ij , B ij is the element in the node admittance matrix; θ ij is the voltage phase angle difference between nodes i and j.

[0099] In addition, each variable needs to satisfy the corresponding inequality constraints.

[0100] For the control variable u, we have:

[0101]

[0102] Among them, P g is the active power output of the generator, P gmax , P gmin V is the upper and lower limits of the active output of the generator, and the specific value is the relevant parameter of the generator; g is the voltage amplitude of the PV node; T is the transformation ratio of the tap-adjustable transformer, and its value is divided into steps of 0.02, that is, T = 0.9, 0.92, …, 1.1.

[0103] For the state variable x, we have:

[0104]

[0105] Among them, S l , P l is the apparent power and active power flowing through the line, S lmax , S lmin , P lmax , P lmin They are the upper and lower limits of the line apparent power and active power, that is, the power limits to ensure stable operation of the line; I l is the line current, I lmax ,I lmin Q is the upper and lower limits of the line current, that is, the current limit to ensure stable operation of the line; g is the reactive power output of the generator, Q gmax , Q gmin It is the upper and lower limits of the reactive power output of the generator, and the specific values ​​are the relevant parameters of the generator.

[0106] b. HPFC self-constraints.

[0107] When the HPFC is operating normally, the nodes of the controlled line need to meet the power balance constraints:

[0108]

[0109] Among them, P is , Q is represents the additional injected power of HPFC to node i.

[0110] At the same time, when calculating the HPFC control variables, it is also necessary to ensure that they are within a reasonable range:

[0111]

[0112] Among them, P njmax , P njminis the upper and lower limits of the active power of the controlled line; Q njmax , Q njmin is the upper and lower limits of reactive power of the controlled line; V nmax 、V nmin is the upper and lower limits of the voltage amplitude at node n; θ nimax ,θ nimin is the upper and lower limits of the voltage phase angle difference between node n and node i; R inmax , R inmin is the upper and lower limits of the compensation resistance of line in; X inmax , X inmin It is the upper and lower limits of the compensation reactance of line in. The specific value is the relevant parameter of the selected controlled line.

[0113] In addition, the calculated HPFC voltage parameters cannot exceed the reasonable range, that is:

[0114]

[0115] Among them, V semax 、V crmax They are the voltage amplitudes of UPFC and ST series sides corresponding to the maximum capacity.

[0116] The specific flow chart of the method is as follows Figure 1 As shown, the following steps are included:

[0117] S1: Input grid data and N-1 expected fault sets, initialize control variables, which include control target values ​​of different HPFC control modes, adjustable generator output, PV node voltage, and tap adjustable transformer ratio;

[0118] S2: Perform power flow calculation of HPFC in constant power control mode. If the calculation result does not meet the constraint conditions, all control parameters are regenerated; if the conditions are met, the values ​​of each objective function are calculated;

[0119] S3: Perform power flow calculation of HPFC in the other three control modes. If the calculation result does not meet the constraint conditions, regenerate the control parameters corresponding to the control mode; if the conditions are met, calculate the values ​​of each objective function;

[0120] S4: Calculate the total objective function, record the individual optimal objective function and the group optimal objective function and their corresponding control variables and HPFC control modes;

[0121] S5: If the number of iterations does not reach the set value, go to S6, otherwise go to S7;

[0122] S6: Update the parameters and speed of the control variables and go to S2;

[0123] S7: Output power flow optimization results and optimal control mode.

[0124] The power flow calculation process of the HPFC in the constant power control mode in step S2 is as follows:

[0125] The constant power control mode of HPFC refers to controlling the voltage source on the series side so that the active and reactive power flows of the series side line reach ideal values.

[0126] The equivalent circuit diagram of HPFC is shown in Figure 2 Among them, the controlled line of the system is the ij branch; V se ,θ se is the voltage amplitude and phase angle of the series side of UPFC; V cr ,θ cr are the voltage amplitude and phase angle of the series side of ST respectively; V k ,θ k (k=i,j,m,n) are the voltage amplitude and phase angle of the corresponding node respectively; are the parallel side current phasors of UPFC and ST respectively; X se , X cr are the equivalent impedances of the series-side coupling transformers of UPFC and ST, respectively; are the current phasors flowing through the UPFC and ST series side respectively; P nj , Q nj are respectively the active and reactive power flows of the controlled line; g L 、b L , B c They are the equivalent conductance and susceptance on the series side of the line and the shunt susceptance of the line respectively.

[0127] The power flow of line nj can be expressed as:

[0128]

[0129] V n ∠θ n =V i ∠θ i +V H ∠θ H (15)

[0130] Among them, V H ,θ H Indicates the voltage amplitude and phase angle of the series side of the HPFC.

[0131] The combined equations (14) and (15) can be used to solve the series side voltage amplitude of the HPFC in the constant power control mode: and phase angle

[0132] For HPFC access lines, there are:

[0133]

[0134] in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the constant power control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the switching position of ST;

[0135] According to the calculation result of formula (16), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

[0136] The power flow calculation process of the HPFC in other control modes in step S3 is as follows:

[0137] Figure 3 It is the voltage phasor diagram of HPFC in different control modes.

[0138] 1) Voltage regulation control mode.

[0139] The voltage regulation control mode of HPFC refers to controlling the voltage amplitude of the HPFC series side when the voltage of the HPFC series side is at the same phase angle as the parallel bus voltage. n =V ref When , we can get:

[0140]

[0141] According to formula (17), the series side voltage amplitude of HPFC in voltage regulation control mode can be obtained as and phase angle

[0142] For HPFC access lines, there are:

[0143]

[0144] in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position.

[0145] According to the calculation result of formula (18), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

[0146] 2) Phase angle adjustment control mode.

[0147] The phase angle regulation control mode of HPFC refers to controlling the phase angle of the series side voltage while keeping the HPFC series side voltage and the parallel bus voltage amplitude the same. Taking the voltage of node i as the reference, V H ∠θ H Decomposed into horizontal component V Hp and the vertical component V Hq , when the voltage phase angle difference between node i and node n is θ ref When , we can get:

[0148]

[0149]

[0150] in, is the phase angle difference between the HPFC series side voltage and the node i voltage.

[0151] The combined equations (19)-(20) can be used to solve the series side voltage amplitude of HPFC in the phase angle regulation control mode: and phase angle

[0152] For HPFC access lines, there are:

[0153]

[0154] in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position.

[0155] According to the calculation result of formula (21), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

[0156] 3) Impedance compensation control mode.

[0157] The impedance compensation control mode of HPFC is to control the ratio of the voltage of the series voltage source to the current flowing through to maintain a constant value to compensate for the impedance of the controlled line. When the HPFC compensation impedance target value is Z ref hour:

[0158]

[0159] in, Indicates the line series current phasor;

[0160] According to formula (22), the series side voltage amplitude of HPFC in impedance compensation control mode can be obtained as and phase angle

[0161] For HPFC access lines, there are:

[0162]

[0163] in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position.

[0164] According to the calculation result of formula (23), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

[0165] In some examples of the present invention, a computer-readable storage medium is also involved, which stores instructions. When the instructions are executed, the above-mentioned power system flow optimization method can be implemented. More specifically, the instructions can be a computer-readable language. The above-mentioned computer can be a general-purpose computer device or a special-purpose computer device. In a specific implementation, the computer can be a desktop, a portable computer, a network server, a PDA (Personal Digital Assistant), a mobile phone, a tablet computer, a wireless terminal device, a communication device or an embedded device. The storage medium can be any available medium that can be accessed by the computer or a data storage device such as a server or a data center that includes one or more available media. For example, the storage medium is, for example, but not limited to, a magnetic medium (for example, a floppy disk, a hard disk, a tape), an optical medium (for example, a digital versatile disc (Digital Versatile Disc, DVD)), or a semiconductor medium (for example, a solid-state drive (SSD)), etc.

[0166] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0167] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for optimizing power flow in a power system taking into account a HPFC control mode, characterized in that: The following steps are involved: S1: construct an optimization model containing control variables, objective functions and constraints; input power grid data and N-1 expected fault sets, and initialize control variables; the control variables include control variables of different HPFC control modes and power system control variables; S2: Perform power flow calculation of HPFC in constant power control mode. If the calculation result does not meet the constraint conditions, all control variables are regenerated; if the conditions are met, the values ​​of each objective function are calculated; S3: Perform power flow calculation of the HPFC in other control modes except the fixed power control mode. If the calculation result does not meet the constraint conditions, regenerate the control variables corresponding to the control mode; if the conditions are met, calculate the values ​​of each objective function; S4: Calculate the total objective function, record the individual optimal objective function and the group optimal objective function and their corresponding control variables and HPFC control modes; S5: If the number of iterations does not reach the set value, go to S6, otherwise go to S7; S6: Update each control variable and go to S2; S7: Output power flow optimization results and optimal control mode; In step S2, the constant power control mode of the HPFC refers to controlling the series side voltage source so that the active and reactive power flows of the series side line reach ideal values; in the constant power control mode, the calculation method of the HPFC control variable includes the following steps: Additional nodes m and n are introduced on line ij, and the additional node m is located between UPFC and ST, and the additional node n is located between ST and line impedance; The power flow of line nj can be expressed as: V n ∠θ n =V i ∠θ i +V H ∠θ H (2) Among them, V k ,θ k (k=i,j,m) represents the voltage amplitude and phase angle of the corresponding node; g L , b L Indicates the series conductance and susceptance of the line; B c Represents the line parallel susceptance; V H ,θ H Indicates the voltage amplitude and phase angle on the HPFC series side; The combined equations (1) and (2) can be used to solve the voltage amplitude of the series side of the HPFC in the constant power control mode: and phase angle For HPFC access lines, there are: in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the constant power control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the switching position of ST; Respectively represent the current phasors flowing through the UPFC and ST series side; X se , X cr denote the series transformer coupling reactance of UPFC and ST respectively; According to the calculation result of formula (3), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

2. The power system power flow optimization method taking into account the HPFC control mode according to claim 1, characterized in that: Other modes include: one or more of a voltage regulation control mode, a phase angle regulation control mode, and an impedance compensation control mode; The voltage regulation control mode refers to controlling the voltage amplitude of the HPFC series side when the voltage of the HPFC series side is at the same phase angle as the parallel bus voltage; The phase angle adjustment control mode is to control the phase angle of the series side voltage while keeping the HPFC series side voltage and the parallel bus voltage amplitude the same; The impedance compensation control mode refers to controlling the voltage of the series-side voltage source and the current flowing therethrough to maintain constant values ​​so as to compensate for the impedance of the controlled line.

3. The power system power flow optimization method taking into account the HPFC control mode according to claim 2, characterized in that: In the voltage regulation control mode, the method for calculating the HPFC control variable comprises the following steps: When the voltage amplitude of node n is V n =V ref When , we can get: According to formula (4), the series side voltage amplitude of HPFC in voltage regulation control mode can be obtained as and phase angle For HPFC access lines, there are: in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position; According to the calculation result of formula (5), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

4. The method for optimizing power flow in a power system taking into account the HPFC control mode according to claim 2, characterized in that: In the phase angle adjustment control mode, the method for calculating the HPFC control variable includes the following steps: Taking the voltage of node i as reference, V H ∠θ H Decomposed into horizontal component V Hp and the vertical component V Hq , when the voltage phase angle difference between node i and node n is θ ref When , we can get: in, is the phase angle difference between the voltage on the HPFC series side and the voltage on node i; The combined equations (6) and (7) can be used to solve the series side voltage amplitude of the HPFC in the phase angle regulation control mode: and phase angle For HPFC access lines, there are: in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position; According to the calculation result of formula (8), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

5. The method for optimizing power flow in a power system taking into account the HPFC control mode according to claim 2, characterized in that: In the impedance compensation control mode, the method for calculating the HPFC control variable includes the following steps: When the HPFC compensation impedance target value is Z ref hour: in, Indicates the line series current phasor; According to formula (9), the series side voltage amplitude of HPFC in impedance compensation control mode can be obtained as and phase angle For HPFC access lines, there are: in, represent the voltage amplitude and phase angle of the series side of UPFC and ST in the voltage regulation control mode, respectively, and and It is a fixed combination, and the specific parameters are related to the ST switching position; According to the calculation result of formula (10), the best switching position of ST is selected, so that minimum, so we can get Specific parameters.

6. The method for optimizing power flow in a power system taking into account the HPFC control mode according to claim 1, characterized in that: The control variables of the power system include: adjustable generator output, generator node voltage and tap adjustable transformer ratio.

7. A computer-readable storage medium storing computer instructions, wherein when the computer instructions are executed, the power system power flow optimization method according to any one of claims 1 to 6 can be implemented.

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