Three-phase four-wire system load flow calculation method and system for alternating-current and direct-current hybrid power grid

Abstract

The invention relates to a three-phase four-wire system load flow calculation method and system for an alternating-current and direct-current hybrid power grid. The method comprises the following steps: acquiring related data of the alternating-current and direct-current hybrid power grid; constructing a three-phase four-wire system power grid matrix model, a direct-current power transmission network matrix model and a voltage source type inverter matrix model; constructing an alternating-current power grid interface equation, a direct-current power grid interface equation and a voltage source type inverter model correction equation; solving the voltage source type inverter model correction equation by using the alternating current power grid interface equation and the direct current power grid interface equation to obtain the correction amount of the voltage source type inverter model variable; substituting the correction of the voltage source inverter model variable into the AC power grid interface equation and the DC power grid interface equation to obtain the correction of the AC power grid variable and the correction of the DC power grid variable; and the solving process is iterated until the unbalance amount of the alternating current and direct current hybrid power grid power equation in the iteration process reaches a preset threshold value, iteration is stopped, and the final correction amount is obtained.

Description

Technical Field

[0001] This application relates to the field of power flow calculation in power systems, and mainly relates to a power flow calculation method and system for a three-phase four-wire AC-DC hybrid power grid. Background Art

[0002] In the current field of re-distribution network simulation research, with the continuous expansion of the scale of power systems and the increasing complexity, the demand for accurate and efficient simulation methods has become more urgent. Currently, the existing methods in this field can be mainly classified into two categories: quasi-steady state models and electromagnetic transient simulations, each with its own unique characteristics and applicable scenarios. Electromagnetic transient simulations can accurately capture various transient phenomena in power systems, such as the electromagnetic processes of lightning strikes, short circuit faults, etc. that change instantaneously, but have a large computational cost. Since it is necessary to perform detailed calculations for each time step within the time domain, this not only requires extremely high computing resources, but also consumes a large amount of time and cost, which to a certain extent limits its wide application in large-scale re-distribution network simulations. Quasi-steady state models have been relatively widely used in the simulation of single-phase power flow in large power grids and the analysis of electromechanical transient stability. By simplifying and approximating the power system, the computational complexity and cost are reduced.

[0003] In terms of phase-segregated power flow, most of the existing research is based on the assumptions of neutral line balance or ideal grounding, and uses four-wire current injection models and linearized three-phase four-wire models. These assumptions and models simplify the calculation of phase-segregated power flow to a certain extent, but there may be a certain deviation from the actual operation of power systems. Especially for the three-phase four-wire power flow algorithm, due to the need to consider the influence of neutral line current and the unbalanced characteristics between the three phases, there are still certain difficulties in engineering implementation and further research and improvement are needed to improve its application effect in actual re-distribution networks.

[0004] As disclosed in the Chinese invention patent with the publication number "CN118630766A", a "Unified Power Flow Calculation Method for AC-DC Hybrid Distribution Network" is disclosed. Specifically, it discloses that "a unified power flow calculation method for AC-DC hybrid distribution network is provided. The method includes: establishing a VSC steady-state model, and establishing a power equation between two adjacent nodes in the AC-DC hybrid distribution network. The power equation is determined according to the transmission mode between the two adjacent nodes, including AC transmission, DC transmission, through a converter and AC / DC transmission; respectively determining the corresponding power balance equation between two adjacent nodes and the droop control equation corresponding to the distributed power sources connected to the nodes according to the power equation; establishing a unified power flow model according to the VSC steady-state model, power equation, power balance equation and droop control equation to determine the node voltage and line power between two adjacent nodes in the AC-DC hybrid distribution network", but this method does not involve relevant content for model correction. After the model is established, the calculation process is relatively fixed, and it is difficult to adjust and optimize the model according to the actual situation or calculation results; in addition, this method does not involve the process of iterative solution, and only determines the node voltage and line power by establishing various equations and models, which may not be able to handle the convergence problem of equation solution well in complex situations. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present application provides a power flow calculation method and system for a three-phase four-wire AC-DC hybrid power grid.

[0006] The technical solution of the present application is as follows:

[0007] On the one hand, the present invention proposes a power flow calculation method for a three-phase four-wire AC-DC hybrid power grid, and the method includes:

[0008] Obtain relevant data of the AC-DC hybrid power grid, including three-phase four-wire distribution network parameters, DC transmission network parameters and voltage source converter parameters; perform power flow calculation for the three-phase four-wire AC-DC hybrid power grid according to the relevant data, and construct a three-phase four-wire grid matrix model, a DC transmission network matrix model and a voltage source converter matrix model;

[0009] Based on the three-phase four-wire grid matrix model, the DC transmission network matrix model and the voltage source converter matrix model, construct a power flow matrix normal form for the AC-DC hybrid power grid, including an AC grid interface equation, a DC grid interface equation and a voltage source converter model correction equation; use the AC grid interface equation and the DC grid interface equation to solve the voltage source converter model correction equation to obtain the correction amount of the voltage source converter model variables; substitute the correction amount of the voltage source converter model variables into the AC grid interface equation and the DC grid interface equation to obtain the correction amount of the AC grid variables and the correction amount of the DC grid variables;

[0010] The iterative solution process is carried out until the imbalance of the AC-DC hybrid power grid power equation in the iterative process reaches a preset threshold, at which point the iteration is stopped, and the correction amounts of the final AC power grid variables and the DC power grid variables are obtained.

[0011] Preferably, the three-phase four-wire distribution network parameters include the complex voltage vectors of all nodes, the amplitude vectors of the node voltages, the phase angle vectors of the node voltages, the active power vectors of the nodes, the deviation vectors of the active power balance equations, the reactive power vectors of the nodes, the deviation vectors of the reactive power balance equations, the active power vectors of the phase nodes, the amplitude vectors of the phase node voltages, the phase angle vectors of the phase node voltages, the deviation vectors of the active power balance equations of the phase nodes, the deviation vectors of the reactive power balance equations of the phase nodes, the phase types of the nodes, the active power vectors injected into the voltage source inverters, the reactive power vectors injected into the voltage source inverters, the deviation amounts of the node voltage phase angle vectors, the active electromagnetic power flowing out of the nodes via the AC power grid, the reactive electromagnetic power flowing out of the nodes via the AC power grid, the first constant term, and the second constant term;

[0012] The DC transmission network parameters include the DC grid node injection current vector, the current vector injected into the DC grid through the voltage source inverter, the DC node voltage vector, the linear correlation coefficient of the correction amount, and the third constant term;

[0013] The parameters of the voltage source inverter include the active power imbalance, the reactive power imbalance, the active power, the reactive power, the system-side voltage, the amplitude of the inverter voltage on the AC side of the converter, the angle by which the inverter voltage lags behind the AC system, the DC side voltage of the converter, the conductance vector of the AC series loop of the converter, the susceptance vector of the AC series loop of the converter, the susceptance vector of the AC parallel loop of the converter, the constant term vector in the linear relationship between the AC active power injection and the voltage amplitude correction of the voltage source inverter, the constant term vector in the linear relationship between the DC grid injection current and the DC side voltage correction of the voltage source inverter, the interface node incidence matrix representing the voltage source inverter to the AC power grid, the interface node incidence matrix from the AC power grid to the voltage source inverter, the interface node incidence matrix of the voltage source inverter to the DC power grid, the interface node incidence matrix of the DC power grid to the voltage source inverter, the imbalance of the control equation of the active power injected by the converter, and the imbalance of the control equation of the inverter voltage of the converter.

[0014] Preferably, a three-phase four-wire grid matrix model, a DC transmission network matrix model, and a voltage source inverter matrix model are constructed. Specifically:

[0015] The three-phase four-wire grid matrix model is expressed by the formula:

[0016]

[0017]

[0018] In the formula, represents the complex nodal admittance matrix; represents the complex nodal admittance sub-matrix between phase-a nodes; G represents the real part of the nodal admittance matrix; B represents the imaginary part of the nodal admittance matrix; represents the complex voltage vector of all nodes; represents the apparent power flowing out of the node; U represents the amplitude vector of the node voltage; θ represents the phase angle vector of the node voltage; P represents the active power vector of the node; ΔP represents the deviation vector of the active power balance equation; Q represents the reactive power vector of the node; ΔQ represents the deviation vector of the reactive power balance equation; j represents the unit imaginary number; P a represents the active power vector of the phase-a node; U a represents the amplitude vector of the voltage of the phase-a node; θ a represents the phase angle phasor of the voltage of the phase-a node; ΔP a represents the deviation vector of the active power balance equation of the phase-a node; ΔQ a represents the deviation vector of the reactive power balance equation of the phase-a node; P e represents the active electromagnetic power flowing out of the node via the AC power grid; Q e represents the reactive electromagnetic power flowing out of the node via the AC power grid; a, b, c, and n represent the phase types of the nodes, that is, the index values of the rows and columns of the nodal admittance sub-matrix; real represents the real part function; imag represents the imaginary part function; conj represents taking the conjugate of the corresponding complex number;

[0019] The matrix model of the DC transmission network is expressed by the formula:

[0020] Δi = i + i vsc -Y d ·su;

[0021] In the formula, Δi represents the change amount of the DC grid node injection current vector; i represents the DC grid node injection current vector; i vsc represents the current vector injected into the DC grid through the voltage source type inverter; Y d represents the DC grid admittance matrix; su represents the DC node voltage vector;

[0022] The matrix model of the voltage source type inverter is expressed by the formula:

[0023]

[0024] In the formula, ΔP a,vsc represents the active power imbalance of the converter phase-a; ΔQ a,vsc represents the reactive power imbalance of the converter phase-a; P a,vsc represents the active power injected by the converter phase-a; Q a,vscRepresents the reactive power injected by phase a of the converter; ΔP d Represents the deviation vector of the active power balance equation of the DC grid; U a,vsc Represents the system-side voltage of phase a of the converter; U d Represents the amplitude of the inverter voltage on the AC side of the converter; δ represents the angle by which the inverter voltage lags behind the AC system; u vsc Represents the DC-side voltage of the converter; G vsc Represents the conductance vector of the AC series circuit of the converter; B vsc Represents the susceptance vector of the AC series circuit of the converter; B f,vsc Represents the susceptance vector of the AC parallel circuit of the converter.

[0025] Preferably, the AC grid interface equation is specifically a linear relationship equation for calculating the correction amounts between the AC grid and the model variables of the voltage source inverter, expressed by the formula:

[0026]

[0027]

[0028] In the formula, P vsc Represents the active power vector injected into the voltage source inverter; Q vsc Represents the reactive power vector injected into the voltage source inverter; K 11 Represents the coefficient matrix of the linear relationship between the change in AC node voltage and the change in active power injected by the inverter; K 12 Represents the coefficient matrix of the linear relationship between the change in AC node voltage and the change in reactive power injected by the inverter; K 21 Represents the coefficient matrix of the linear relationship between the change in DC node voltage and the change in active power injected by the inverter; K 22 Represents the coefficient matrix of the linear relationship between the change in DC node voltage and the change in reactive power injected by the inverter; L 1 Represents the first constant term; L 2 Represents the second constant term.

[0029] Preferably, the DC grid interface equation is specifically a linear relationship equation for calculating the correction amounts between the DC grid and the model variables of the voltage source inverter, expressed by the formula:

[0030] dΔi = di vsc -Y d ·d(su);

[0031] d(su) = N + M * d(i vsc );

[0032] N = -(Y d ) -1 *dΔi;

[0033] M = (Y d ) -1 ;

[0034] In the formula, M represents the linear correlation coefficient of the correction amount; N represents the third constant term.

[0035] Preferably, the voltage source inverter model correction equation is solved by using the AC grid interface equation and the DC grid interface equation, and is expressed by the formula:

[0036]

[0037] KS 1 = C cs K 11 C sc ;

[0038] KS 2 = C cs K 12 C sc ;

[0039] CS = C cs L 1 ;

[0040] C cs = (C sc ) T ;

[0041] KD = C cd *M*C dc ;

[0042] CD = C cd *N;

[0043] C cd = (C dc ) T ;

[0044] In the formula, KS 1 represents the coefficient matrix part in the linear relationship between the AC active power injection and the voltage amplitude correction amount of the voltage source inverter; KS 2 represents the coefficient matrix part in the linear relationship between the AC reactive power injection and the voltage amplitude correction amount of the voltage source inverter; CS represents the constant term vector in the linear relationship between the AC active power injection and the voltage amplitude correction amount of the voltage source inverter; KD represents the coefficient matrix part in the linear relationship between the DC grid injection current and the DC side voltage correction amount of the voltage source inverter; CD represents the constant term vector in the linear relationship between the DC grid injection current and the DC side voltage correction amount of the voltage source inverter; C cs represents the interface node incidence matrix from the voltage source inverter to the AC grid; Csc Denote the incidence matrix of the interface nodes from the AC power grid to the voltage source inverter; C cd Denote the incidence matrix of the interface nodes from the voltage source inverter to the DC power grid; C dc Denote the incidence matrix of the interface nodes from the DC power grid to the voltage source inverter; I represents the unit diagonal matrix; ΔP set Denote the imbalance of the active power injection control equation of the converter; ΔU d set Denote the imbalance of the control equation of the inverter voltage of the converter; T represents the transpose operation.

[0045] Preferably, obtain the correction amounts of the final AC power grid variables and the DC power grid variables, and the correction amounts of the AC power grid variables and the DC power grid variables are specifically recalculated by using the AC power grid interface equation and the DC power grid interface equation.

[0046] On the other hand, the present invention also proposes a power flow calculation system for a three-phase four-wire AC-DC hybrid power grid, and the system includes a data acquisition module, an equation construction module, a correction amount solving module, and a result output module, wherein:

[0047] The data acquisition module is used to acquire the relevant data of the AC-DC hybrid power grid, including the parameters of the three-phase four-wire distribution network, the parameters of the DC transmission network, and the parameters of the voltage source inverter; and transmit the relevant data to the equation construction module;

[0048] The equation construction module is used to perform the power flow calculation of the three-phase four-wire AC-DC hybrid power grid according to the relevant data, construct a three-phase four-wire power grid matrix model, a DC transmission network matrix model, and a voltage source inverter matrix model; and construct a power flow matrix paradigm of the AC-DC hybrid power grid based on the three-phase four-wire power grid matrix model, the DC transmission network matrix model, and the voltage source inverter matrix model, including an AC power grid interface equation, a DC power grid interface equation, and a voltage source inverter model correction equation;

[0049] The correction amount solving module is used to solve the voltage source inverter model correction equation by using the AC power grid interface equation and the DC power grid interface equation to obtain the correction amounts of the voltage source inverter model variables; substitute the correction amounts of the voltage source inverter model variables into the AC power grid interface equation and the DC power grid interface equation to obtain the correction amounts of the AC power grid variables and the DC power grid variables; and perform an iterative solution process until the imbalance of the AC-DC hybrid power grid power equation in the iterative process reaches a preset threshold, then stop the iteration, and obtain the correction amounts of the final AC power grid variables and the DC power grid variables;

[0050] The result output module is used to display the correction amounts of all variables.

[0051] On the other hand, the present invention further provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, a power flow calculation method for a three-phase four-wire AC-DC hybrid power grid as described in any embodiment of the present invention is implemented.

[0052] On the other hand, the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, a power flow calculation method for a three-phase four-wire AC-DC hybrid power grid as described in any embodiment of the present invention is implemented.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1) The present invention provides a power flow calculation method and system for a three-phase four-wire AC-DC hybrid power grid, respectively constructing a three-phase four-wire power grid matrix model, a DC transmission network matrix model, and a voltage source inverter matrix model, modularizing the complex power grid system, improving the flexibility of model construction, and enhancing the adaptability of the model to AC-DC hybrid power grids with different structures and parameters;

[0055] 2) The present invention provides a power flow calculation method and system for a three-phase four-wire AC-DC hybrid power grid. By constructing a power flow matrix normal form of the AC-DC hybrid power grid, solving the inverter model correction equation using the interface equation, and through an iterative solution process until the residual value reaches a preset threshold, this calculation method improves the accuracy and efficiency of the calculation results;

[0056] 3) The present invention provides a power flow calculation method and system for a three-phase four-wire AC-DC hybrid power grid. The modular matrix model construction method and the iterative correction calculation process make it easier to integrate new power grid components, operation modes, or control strategies into the existing model when facing them, improving the flexibility of model expansion and the application convenience of an efficient solver. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a flowchart of the method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] The following describes the specific embodiments of the present invention to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions made using the concept of the present invention are within the scope of protection.

[0059] The present invention provides the following technical solution: A power flow calculation method and system for a three-phase four-wire AC-DC hybrid power grid.

[0060] Embodiment 1

[0061] Specifically refer to Figure 1 , this embodiment provides a power flow calculation method for a three-phase four-wire AC-DC hybrid power grid. The specific steps include:

[0062] S1. Obtain relevant data of the AC-DC hybrid power grid, including three-phase four-wire distribution network parameters, DC transmission network parameters, and voltage source inverter parameters;

[0063] The three-phase four-wire distribution network parameters include the voltage complex vector of all nodes, the amplitude vector of the node voltage, the phase angle vector of the node voltage, the active power vector of the node, the deviation vector of the active power balance equation, the reactive power vector of the node, the deviation vector of the reactive power balance equation, the active power vector of the phase node, the voltage amplitude vector of the phase node, the voltage phase angle phasor of the phase node, the deviation vector of the active power balance equation of the phase node, the deviation vector of the reactive power balance equation of the phase node, the phase type of the node, the active power vector injected into the voltage source inverter, the reactive power vector injected into the voltage source inverter, the deviation quantity of the node voltage phase angle vector, the active electromagnetic power flowing out of the node via the AC power grid, the reactive electromagnetic power flowing out of the node via the AC power grid, the first constant term, and the second constant term;

[0064] The DC transmission network parameters include the DC grid node injection current vector, the current vector injected into the DC grid via the voltage source inverter, the DC node voltage vector, the linear correlation coefficient of the correction quantity, and the third constant term;

[0065] The voltage source inverter parameters include the active power imbalance, the reactive power imbalance, the active power, the reactive power, the system-side voltage, the amplitude of the inverter voltage on the AC side of the converter, the angle by which the inverter voltage of the converter lags behind the AC system, the DC-side voltage of the converter, the conductance vector of the AC series loop of the converter, the susceptance vector of the AC series loop of the converter, the susceptance vector of the AC parallel loop of the converter, the constant term vector in the linear relationship between the AC active power injection and the voltage amplitude correction of the voltage source inverter, the constant term vector in the linear relationship between the DC grid injection current and the DC-side voltage correction of the voltage source inverter, the interface node incidence matrix representing the voltage source inverter to the AC power grid, the interface node incidence matrix from the AC power grid to the voltage source inverter, the interface node incidence matrix from the voltage source inverter to the DC power grid, the interface node incidence matrix from the DC power grid to the voltage source inverter, the imbalance of the control equation of the active power injected by the converter, and the imbalance of the control equation of the inverter voltage of the converter;

[0066] S2. Conduct power flow calculation for the three-phase four-wire AC / DC hybrid power grid based on the relevant data, and construct a three-phase four-wire power grid matrix model, a DC transmission network matrix model, and a voltage source inverter matrix model;

[0067] S21. The three-phase four-wire power grid matrix model is expressed by the formula:

[0068]

[0069]

[0070] In the formula, represents the complex node admittance matrix; represents the complex node admittance sub-matrix between the a-phase node and the a-phase node; G represents the real part of the node admittance matrix; B represents the imaginary part of the node admittance matrix; U represents the complex voltage vector of all nodes; represents the apparent power flowing out of the node; U represents the amplitude vector of the node voltage; θ represents the phase angle vector of the node voltage; P represents the active power vector of the node; ΔP represents the deviation vector of the active power balance equation; Q represents the reactive power vector of the node; ΔQ represents the deviation vector of the reactive power balance equation; j represents the unit imaginary number; P a represents the active power vector of the a-phase node; U a represents the amplitude vector of the a-phase node voltage; θ a represents the phase angle phasor of the a-phase node voltage; ΔP a represents the deviation vector of the active power balance equation of the a-phase node; ΔQ a represents the deviation vector of the reactive power balance equation of the a-phase node; P e represents the active electromagnetic power flowing out of the node via the AC power grid; Q e represents the reactive electromagnetic power flowing out of the node via the AC power grid; a, b, c, and n represent the phase types of the nodes, that is, the index values of the rows and columns of the node admittance sub-matrix; real represents the real part function; imag represents the imaginary part function; conj represents taking the conjugate of the corresponding complex number;

[0071] S22. The DC transmission network matrix model is expressed by the formula:

[0072] Δi = i + i vsc -Y d ·su;

[0073] In the formula, Δi represents the change amount of the DC power grid node injection current vector; i represents the DC power grid node injection current vector; i vsc represents the current vector injected into the DC power grid via the voltage source inverter; Y d represents the DC power grid admittance matrix; su represents the DC node voltage vector;

[0074] S23. The matrix model of the voltage source inverter is expressed by the formula:

[0075]

[0076] In the formula, ΔP a,vsc represents the active power imbalance of phase a of the converter; ΔQ a,vsc represents the reactive power imbalance of phase a of the converter; P a,vsc represents the active power injected by phase a of the converter; Q a,vsc represents the reactive power injected by phase a of the converter; ΔP d represents the deviation vector of the active power balance equation of the DC grid; U a,vsc represents the system-side voltage of phase a of the converter; U d represents the amplitude of the inverter voltage on the AC side of the converter; δ represents the angle by which the inverter voltage lags behind the AC system; u vsc represents the DC-side voltage of the converter; G vsc represents the conductance vector of the AC series loop of the converter; B vsc represents the susceptance vector of the AC series loop of the converter; B f,vsc represents the susceptance vector of the AC parallel loop of the converter;

[0077] S3. Construct the power flow matrix normal form of the AC-DC hybrid grid, including the AC grid interface equation, the DC grid interface equation, and the modified equation of the voltage source inverter model;

[0078] S31. The AC grid interface equation is specifically a linear relationship equation for calculating the correction amount between the AC grid and the variables of the voltage source inverter model, and is expressed by the formula:

[0079]

[0080] In the formula, P vsc represents the active power vector injected into the voltage source inverter; Q vsc represents the reactive power vector injected into the voltage source inverter; K 11 represents the coefficient matrix of the linear relationship between the change in AC node voltage and the change in active power injected by the inverter; K 12 represents the coefficient matrix of the linear relationship between the change in AC node voltage and the change in reactive power injected by the inverter; K 21 represents the coefficient matrix of the linear relationship between the change in DC node voltage and the change in active power injected by the inverter; K 22 represents the coefficient matrix of the linear relationship between the change in DC node voltage and the change in reactive power injected by the inverter; L 1 represents the first constant term; L 2 represents the second constant term;

[0081] S32. The DC grid interface equation is specifically a linear relationship equation for calculating the correction amounts of the DC grid and the model variables of the voltage source inverter, which is expressed by the formula:

[0082] dΔi = di vsc -Y d ·d(su);

[0083] d(su) = N + M*d(i vsc );

[0084] N = -(Y d ) -1 *dΔi;

[0085] M = (Y d ) -1 ;

[0086] In the formula, M represents the linear correlation coefficient of the correction amount; N represents the third constant term;

[0087] S4. Use the AC grid interface equation and the DC grid interface equation to solve the voltage source inverter model correction equation to obtain the correction amounts of the voltage source inverter model variables, which is expressed by the formula:

[0088]

[0089] KS 1 = C cs K 11 C sc ;

[0090] KS 2 = C cs K 12 C sc ;

[0091] CS = C cs L 1 ;

[0092] C cs = (C sc ) T ;

[0093] KD = C cd *M*C dc ;

[0094] CD = C cd *N;

[0095] C cd = (C dc ) T ;

[0096] In the formula, KS1 Denotes the coefficient matrix part in the linear relationship between the AC active injection power and the correction amount of the AC side voltage amplitude of the voltage source inverter; KS 2 Denotes the coefficient matrix part in the linear relationship between the AC reactive injection power and the voltage amplitude correction amount of the voltage source inverter; CS denotes the constant term vector in the linear relationship between the AC active injection power and the voltage amplitude correction amount of the voltage source inverter; KD denotes the coefficient matrix part in the linear relationship between the DC grid injection current and the DC side voltage correction amount of the voltage source inverter; CD denotes the constant term vector in the linear relationship between the DC grid injection current and the DC side voltage correction amount of the voltage source inverter; C cs Denotes the interface node incidence matrix from the voltage source inverter to the AC grid; C sc Denotes the interface node incidence matrix from the AC grid to the voltage source inverter; C cd Denotes the interface node incidence matrix from the voltage source inverter to the DC grid; C dc Denotes the interface node incidence matrix from the DC grid to the voltage source inverter; I denotes the unit diagonal matrix; ΔP set Denotes the imbalance of the active power injection control equation of the converter; ΔU d set Denotes the imbalance of the control equation of the inverter voltage of the converter; T denotes the transpose operation

[0097] S5. Substitute the correction amounts of the model variables of the voltage source inverter into the AC grid interface equation and the DC grid interface equation to obtain the correction amounts of the AC grid variables and the DC grid variables;

[0098] S6. Iterative solution process, until the imbalance of the AC-DC hybrid grid power equation in the iterative process reaches a preset threshold, stop the iteration, and obtain the final correction amounts of the AC grid variables and the DC grid variables. The correction amounts of the AC grid variables and the DC grid variables are specifically recalculated using the AC grid interface equation and the DC grid interface equation.

[0099] Embodiment 2

[0100] This embodiment provides a power flow calculation system for a three-phase four-wire AC-DC hybrid grid. The system includes a data acquisition module, an equation construction module, a correction amount solution module, and a result output module, where:

[0101] The data acquisition module is used to acquire relevant data of the AC-DC hybrid grid, including three-phase four-wire distribution network parameters, DC transmission network parameters, and voltage source inverter parameters; and transmit the relevant data to the equation construction module;

[0102] The equation construction module is used to perform power flow calculation for a three-phase four-wire AC-DC hybrid power grid based on the relevant data, construct a three-phase four-wire power grid matrix model, a DC power transmission network matrix model, and a voltage source inverter matrix model; construct an AC-DC hybrid power grid power flow matrix paradigm based on the three-phase four-wire power grid matrix model, the DC power transmission network matrix model, and the voltage source inverter matrix model, including an AC power grid interface equation, a DC power grid interface equation, and a voltage source inverter model correction equation;

[0103] The correction amount solving module is used to solve the voltage source inverter model correction equation by using the AC power grid interface equation and the DC power grid interface equation to obtain the correction amount of the voltage source inverter model variables; substitute the correction amount of the voltage source inverter model variables into the AC power grid interface equation and the DC power grid interface equation to obtain the correction amount of the AC power grid variables and the correction amount of the DC power grid variables; perform an iterative solution process until the imbalance of the AC-DC hybrid power grid power equation in the iterative process reaches a preset threshold, then stop the iteration to obtain the final correction amount of the AC power grid variables and the correction amount of the DC power grid variables;

[0104] The result output module is used to display the correction amounts of all variables.

[0105] Embodiment 3

[0106] This embodiment provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements a power flow calculation method for a three-phase four-wire AC-DC hybrid power grid as described in any embodiment of the present invention.

[0107] Embodiment 4

[0108] This embodiment provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, it implements a power flow calculation method for a three-phase four-wire AC-DC hybrid power grid as described in any embodiment of the present invention.

[0109] It should be noted that the systems, electronic devices, and computer-readable storage media described in the present invention are all based on the same principle as the method described in Embodiment 1, and will not be elaborated here.

[0110] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid, characterized in that: The method comprises: Acquire relevant data of the AC / DC hybrid power grid, including three-phase four-wire distribution network parameters, DC transmission network parameters and voltage source inverter parameters; perform power flow calculation of the three-phase four-wire AC / DC hybrid power grid according to the relevant data, and construct a three-phase four-wire power grid matrix model, a DC transmission network matrix model and a voltage source inverter matrix model; Based on the three-phase four-wire power grid matrix model, the DC power transmission network matrix model and the voltage source inverter matrix model, an AC / DC hybrid power grid power flow matrix paradigm is constructed, including an AC power grid interface equation, a DC power grid interface equation and a voltage source inverter model correction equation; the voltage source inverter model correction equation is solved by using the AC power grid interface equation and the DC power grid interface equation to obtain correction values ​​of the voltage source inverter model variables; the correction values ​​of the voltage source inverter model variables are substituted into the AC power grid interface equation and the DC power grid interface equation to obtain correction values ​​of the AC power grid variables and correction values ​​of the DC power grid variables; The iterative solution process is performed until the unbalanced amount of the AC / DC hybrid power grid power equation in the iterative process reaches a preset threshold value, then the iteration is stopped to obtain the final correction amount of the AC grid variable and the correction amount of the DC grid variable.

2. The method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid according to claim 1, characterized in that: The three-phase four-wire power distribution network parameters include the voltage complex vectors of all nodes, the node voltage amplitude vectors, the node voltage phase angle vectors, the node active power vectors, the active power balance equation deviation vectors, the node reactive power vectors, the active power balance equation deviation vectors, the phase node active power vectors, the phase node voltage amplitude vectors, the phase node voltage phase angle phasors, the phase node active power balance equation deviation vectors, the phase node reactive power balance equation deviation vectors, the node phases, the active power vectors of the injected voltage source inverters, the reactive power vectors of the injected voltage source inverters, the node voltage phase angle vector deviations, the active electromagnetic power flowing out of the nodes via the AC power grid, the reactive electromagnetic power flowing out of the nodes via the AC power grid, the first constant term and the second constant term; The DC power transmission network parameters include a DC grid node injection current vector, a current vector injected into the DC grid via a voltage source inverter, a DC node voltage vector, a linear correlation coefficient of a correction amount, and a third constant term; The voltage source inverter parameters include active power unbalance, reactive power unbalance, active power, reactive power, system side voltage, amplitude of inverter voltage on the AC side of the converter, angle of inverter voltage lagging behind the AC system, DC side voltage of the converter, current conduction vector of the AC series circuit of the converter, susceptance vector of the AC series circuit of the converter, susceptance vector of the AC parallel circuit of the converter, constant term vector in the linear relationship between AC active injection power and voltage source inverter voltage amplitude correction, constant term vector in the linear relationship between DC grid injection current and DC side voltage correction of the voltage source inverter, interface node association matrix representing voltage source inverter to AC grid, interface node association matrix representing AC grid to voltage source inverter, interface node association matrix representing voltage source inverter to DC grid, interface node association matrix representing DC grid to voltage source inverter, unbalanced amount of control equation of active power injection of converter and unbalanced amount of control equation of inverter voltage.

3. The method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid according to claim 1, characterized in that: Construct a three-phase four-wire power grid matrix model, a DC transmission network matrix model and a voltage source inverter matrix model, specifically: The three-phase four-wire power grid matrix model is expressed as follows: In the formula, represents the complex node admittance matrix; represents the complex node admittance submatrix between the a-phase node and the a-phase node; G represents the real part of the node admittance matrix; B represents the imaginary part of the node admittance matrix; represents the complex vector of voltages at all nodes; represents the apparent power flowing out of the node; U represents the amplitude vector of the node voltage; θ represents the phase angle vector of the node voltage; P represents the active power vector of the node; ΔP represents the deviation vector of the active power balance equation; Q represents the reactive power vector of the node; ΔQ represents the deviation vector of the active power balance equation; j represents the unit imaginary number; P a Represents the active vector of phase a node; U a represents the voltage amplitude vector of the a-phase node; θ a Represents the voltage phase angle phasor of phase a node; ΔP a Represents the deviation vector of the active power balance equation of phase a node; ΔQ a represents the deviation vector of the reactive power balance equation of phase a node; P e Represents the active electromagnetic power flowing out of the node through the AC power grid; Q e represents the reactive electromagnetic power flowing out of the node through the AC power grid; a, b, c and n represent the phase difference of the node, that is, the index value of the row and column of the node admittance submatrix; real represents the real part function; imag represents the imaginary part function; conj represents taking the conjugate of the corresponding complex number; The DC transmission network matrix model is expressed as follows: Δi=i+i vsc -Y d ·with; Where Δi represents the change of the current vector injected into the DC grid node; i represents the current vector injected into the DC grid node; i vsc represents the current vector injected into the DC grid through the voltage source inverter; Y d represents the DC grid admittance matrix; su represents the DC node voltage vector; The voltage source inverter matrix model is expressed as follows: In the formula, ΔP a,vsc Indicates the active power imbalance of phase a of the converter; ΔQ a,vsc Indicates the reactive power unbalance of phase a of the converter; P a,vsc Indicates the active power injected into phase a of the converter; Q a,vsc Represents the reactive power injected into phase a of the converter; ΔP d Represents the deviation vector of the active power balance equation of the DC power grid; U a,vsc Indicates the system side voltage of phase a of the converter; U d represents the amplitude of the inverter voltage on the AC side of the converter; δ represents the angle at which the inverter voltage lags behind the AC system; u vsc Indicates the DC side voltage of the converter; G vsc Indicates the current conduction vector of the AC series circuit of the converter; B vsc Represents the susceptance vector of the AC series circuit of the converter; B f,vsc Represents the susceptance vector of the converter AC parallel circuit.

4. The method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid according to claim 1, characterized in that: The AC grid interface equation is specifically a linear relationship between the correction amount of the AC grid and the voltage source inverter model variable, which is expressed as: Where P vsc represents the active power vector injected into the voltage source inverter; Q vsc represents the reactive power vector injected into the voltage source inverter; K 11 K is the coefficient matrix representing the linear relationship between the change in AC node voltage and the change in active power injected by the inverter; 12 K is the coefficient matrix representing the linear relationship between the change in AC node voltage and the change in reactive power injected by the inverter; 21 K is the coefficient matrix representing the linear relationship between the DC node voltage change and the inverter injected active power change; 22 The coefficient matrix representing the linear relationship between the change in DC node voltage and the change in reactive power injected by the inverter; L1 represents the first constant term; L2 represents the second constant term.

5. The method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid according to claim 1, characterized in that: The DC grid interface equation is specifically a linear relationship between the correction amount of the DC grid and the voltage source inverter model variable, which is expressed as: dΔi=d(i vsc )-Y d ·d(su)? d(su)=N+M*d(i vsc ): N=-(Y d ) -1 *dΔi; M=(Y d ) -1 ; Wherein, M represents the linear correlation coefficient of the correction amount; N represents the third constant term.

6. The method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid according to claim 1, characterized in that: The AC grid interface equation and the DC grid interface equation are used to solve the voltage source inverter model correction equation, which is expressed as: KS1=C cs K 11 C sc ; KS2=C cs K 12 C sc ; CS=C cs L1; C cs =(C sc ) T ; KD=C cd *M*C dc ; CD=C cd *N; C cd =(C dc ) T ; Wherein, KS1 represents the coefficient matrix part of the linear relationship between the AC active injection power and the voltage amplitude correction amount of the AC side voltage of the voltage source inverter; KS2 represents the coefficient matrix part of the linear relationship between the AC reactive injection power and the voltage amplitude correction amount of the voltage source inverter; CS represents the constant term vector in the linear relationship between the AC active injection power and the voltage amplitude correction of the voltage source inverter; K D represents the coefficient matrix part of the linear relationship between the DC grid injection current and the DC side voltage correction value of the voltage source inverter; CD represents the constant term vector in the linear relationship between the DC grid injection current and the DC side voltage correction of the voltage source inverter; C cs represents the interface node association matrix from the voltage source inverter to the AC grid; C sc represents the interface node association matrix from AC grid to voltage source inverter; C cd represents the interface node association matrix from the voltage source inverter to the DC grid; C dc represents the interface node association matrix from the DC grid to the voltage source inverter; I represents the unit diagonal matrix; ΔP set It represents the unbalanced quantity injected into the active power control equation of the converter; ΔQ d set It represents the unbalanced quantity of the control equation of the inverter voltage; T represents the transposition operation.

7. The method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid according to claim 1, characterized in that: The final correction amount of the AC grid variable and the correction amount of the DC grid variable are obtained, and the correction amount of the AC grid variable and the correction amount of the DC grid variable are specifically obtained by recalculating using the AC grid interface equation and the DC grid interface equation.

8. A power flow calculation system for a three-phase four-wire AC / DC hybrid power grid, characterized in that: The system includes a data acquisition module, an equation building module, a correction amount solving module and a result output module, wherein: The data acquisition module is used to acquire relevant data of the AC / DC hybrid power grid, including three-phase four-wire power distribution network parameters, DC transmission network parameters and voltage source inverter parameters; and transmit the relevant data to the equation construction module; The equation construction module is used to perform power flow calculation of the three-phase four-wire system of the AC / DC hybrid power grid according to the relevant data, and to construct a three-phase four-wire power grid matrix model, a DC power transmission network matrix model, and a voltage source inverter matrix model; based on the three-phase four-wire power grid matrix model, the DC power transmission network matrix model, and the voltage source inverter matrix model, an AC / DC hybrid power grid power flow matrix paradigm is constructed, including an AC power grid interface equation, a DC power grid interface equation, and a voltage source inverter model correction equation; The correction value solving module is used to solve the voltage source inverter model correction equation using the AC grid interface equation and the DC grid interface equation to obtain the correction value of the voltage source inverter model variable; substitute the correction value of the voltage source inverter model variable into the AC grid interface equation and the DC grid interface equation to obtain the correction value of the AC grid variable and the correction value of the DC grid variable; iterate the solving process until the unbalanced amount of the AC / DC hybrid power grid power equation in the iterative process reaches a preset threshold, then stop the iteration, and obtain the final correction value of the AC grid variable and the correction value of the DC grid variable; The result output module is used to display the correction values ​​of all variables.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid as described in any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method for calculating power flow of a three-phase four-wire AC / DC hybrid power grid as claimed in any one of claims 1 to 7 is implemented.

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