Distributed power supply grid-connected power flow analysis and prediction method

Abstract

The invention relates to a distributed power supply grid-connected power flow analysis and prediction method, and belongs to the technical field of distributed power supply grid connection. The method comprises the following steps: acquiring information of each distributed power supply node according to a power grid network topology structure, selecting one distributed power supply node as a voltage reference node, and initializing the frequency and voltage of each distributed power supply node; solving current based on the information of each distributed power supply node; solving voltage based on the information of each distributed power supply node; updating the reference voltage and the reference frequency; and judging whether the voltage value of each distributed power supply node reaches a convergence condition or not. The method can accurately calculate and analyze the power flow distribution of the power system after grid connection of the distributed power supply, and timely discover and prevent potential voltage fluctuation and power imbalance problems, thereby improving the stability of the power system.

Description

Technical Field

[0001] The present invention belongs to the technical field of distributed power grid connection, and particularly relates to a method for analyzing and predicting the power flow of distributed power grid connection. Background Technique

[0002] With the transformation of the global energy structure and the rapid development of renewable energy, the access ratio of distributed generation (DG) in the power system is increasing day by day. Distributed power mainly includes wind power generation, photovoltaic power generation, fuel cells, etc. They are connected to the distribution network through devices such as inverters, turning the traditional distribution network with unidirectional flow and passive network characteristics into an intelligent grid with bidirectional power flow and active network characteristics. This transformation not only brings diversity and flexibility in energy utilization, but also poses new challenges to the power flow analysis, stable operation and power quality control of the power system.

[0003] Traditional power flow calculation methods are mainly based on centralized calculation models, which require collecting power information of the entire network and performing calculations on the entire network. However, in the case of a large number of distributed power accesses, the number of power source nodes in the power system increases, and the current and voltage distributions become more complex. Traditional power flow calculation methods can no longer accurately calculate the voltage and current of each node.

[0004] Therefore, how to overcome the deficiencies of the existing technology is an urgent problem to be solved in the current technical field of distributed power grid connection. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies of the existing technology and provide a method for analyzing and predicting the power flow of distributed power grid connection, which can accurately analyze and predict the distributed power grid connection scenario, and provide strong technical support and decision-making basis for the planning, dispatching and operation of the power system.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for analyzing and predicting the power flow of distributed power grid connection includes the following steps:

[0008] Step 1: Obtain the information of each distributed power node according to the grid network topology structure, select a distributed power node as the voltage reference node, and initialize the frequency and voltage of each distributed power node; wherein, the distributed power adopts droop control, and the information of each distributed power node includes the active power and reactive power output by the distributed power.

[0009] Step 2: Solve the current based on the information of each distributed power node.

[0010] Step 3: Solve the voltage based on the information of each distributed power node.

[0011] Step 4, update the reference voltage and reference frequency;

[0012] Step 5, determine whether the voltage values of each distributed power generation node reach the convergence condition. If so, stop the iteration and the calculation ends; if not, return to Step 2 and continue the iteration.

[0013] Furthermore, preferably, in Step 1, the specific method for initializing the frequency is: synchronize the output frequencies of all distributed power generation nodes with the grid reference frequency.

[0014] Furthermore, preferably, in Step 1, the specific method for initializing the voltage is: adjust the voltages of all distributed power generation nodes to within the range of ±5% deviation from the standard voltage.

[0015] Furthermore, preferably, in Step 1, the specific method for the distributed power generation to adopt droop control is as follows:

[0016] The droop control model for power flow calculation is as follows:

[0017]

[0018] where m pi , n qi are the droop coefficients corresponding to the active power - frequency and reactive power - voltage droop controls of the i-th distributed power generation respectively, P gi , Q gi are the output active power and output reactive power of the i-th distributed power generation respectively, are the reference active power and reference reactive power of the i-th distributed power generation respectively, w and w0 are the actual frequency and reference frequency defined by the i-th distributed power generation node, |V i | and V0| are the actual voltage amplitude and reference voltage amplitude of the i-th distributed power generation node respectively;

[0019] Control is performed using the described droop control model.

[0020] Furthermore, preferably, the specific method for Step 2 is:

[0021] Calculate the complex power injected into each distributed power generation node:

[0022]

[0023] where P li , Q li are the output active load and output reactive load of the i-th distributed power generation respectively; S i represents the complex power injected into the i-th distributed power generation node;

[0024] Calculate the current \(I\) of the \(i\)-th distributed power generation node based on complex power i :

[0025]

[0026] wherein, \(*\) represents complex number operation, \(V\) i represents the voltage of the \(i\)-th distributed power generation node;

[0027] From the load node to the reference node, sum the currents of the distributed power generation nodes to calculate the branch current matrix \([I\) ij :

[0028] [I\) ij =(A\) T ) -1 [I\) i ;

[0029] wherein, \([I\) i represents the matrix composed of the currents \(I\) i of the distributed power generation nodes, \(A\) is the incidence matrix, \(A\) T is the transpose of the incidence matrix, and the order of the incidence matrix \(A\) is \(N\) b ×\(N\), wherein, \(N\) b and \(N\) respectively represent the number of distributed power generation nodes and the number of branch currents;

[0030] The element \(a\) ij in the matrix \(A\) is:

[0031] (1) \(a\) ij =+1, indicating that the \(j\)-th branch is associated with the \(i\)-th node, and the branch direction leaves the node \(i\);

[0032] (2) \(a\) ij =-1, indicating that the \(j\)-th branch is associated with the \(i\)-th node, and the branch direction points to the node \(i\);

[0033] (3) \(a\) ij =0, indicating that the \(j\)-th branch is not associated with the \(i\)-th node.

[0034] Furthermore, preferably, the specific method of step three is:

[0035] [V] k+1 =(1 - β)[V] k +β([V\) REF -(A) -1 diag(Z\) ij )[I\) ij );

[0036] wherein, \([V] k+1 represents the voltage of the \((k + 1)\)-th iteration; \([V] krepresents the voltage at the k-th iteration; β represents the deceleration factor; diag(Z ij ) represents the diagonal matrix of branch impedance; [V REF represents the maximum voltage for grid connection of the preset distributed power source.

[0037] Furthermore, preferably, the value range of β is (0, 1).

[0038] Furthermore, preferably, the specific method of step four is as follows:

[0039] Automatic voltage control AVC system correction:

[0040] The AVC system calculates the voltage control sensitivity matrix by real-time monitoring of the distribution of grid voltage and reactive power;

[0041] According to the situation of voltage over-limit nodes, the AVC system corrects the voltage of voltage over-limit nodes in each control area;

[0042] If a certain control area fails to be successfully corrected due to excessive over-limit quantity or too many over-limit nodes of voltage over-limit nodes, the AVC system will try to minimize the voltage over-limit nodes of the entire system through the adjustment of other areas.

[0043] Furthermore, preferably, the specific method of step four is as follows:

[0044] When the voltage values of each node gradually tend to be stable, that is, the voltage difference between two adjacent iterations is within the preset range, it is determined that the voltage values of each distributed power source node reach the convergence condition.

[0045] In step one of the present invention, the specific method of frequency initialization is as follows:

[0046] (1) Standard frequency setting

[0047] Reference value: Usually set to 50Hz (China standard) or 60Hz (standards of some countries / regions).

[0048] Synchronization requirement: All distributed power source nodes need to be synchronized with the grid reference frequency to avoid power oscillation or equipment damage caused by frequency deviation.

[0049] (2) Initialization step

[0050] Measure the grid frequency: Obtain the actual grid frequency through a phase-locked loop (PLL) or a frequency sensor.

[0051] Adjust the power output: The distributed power source (such as an inverter) adjusts the output frequency to match the grid frequency.

[0052] Dynamic tracking: During grid-connected operation, continuously monitor and adjust the frequency to ensure synchronization with the grid.

[0053] (3) Example

[0054] If the grid frequency is 49.9 Hz, the distributed power source needs to adjust the output frequency to 49.9 Hz instead of fixing it at 50 Hz.

[0055] In step one of the present invention, the specific method of voltage initialization is as follows:

[0056] (1) Standard voltage setting

[0057] Reference value: Set according to the voltage level, such as 10 kV, 35 kV or 0.4 kV (low-voltage distribution).

[0058] Allowable deviation: Usually allow a deviation of ±5% (for example, 10 kV corresponds to 9.5 kV to 10.5 kV).

[0059] (2) Initialization steps

[0060] Measure the node voltage: Obtain the actual voltage of the node through a voltage sensor.

[0061] Adjust the reactive power: Adjust the node voltage to the reference value through a reactive power compensation device (such as a capacitor, reactor) or inverter reactive power control.

[0062] Hierarchical control:

[0063] Primary control: Local automatic voltage regulation (AVR) quickly responds to voltage deviation.

[0064] Secondary control: Coordinate the reactive power distribution of multiple nodes through communication to optimize the global voltage distribution.

[0065] (3) Example

[0066] If the voltage of a certain node is 9.8 kV (lower than the 10 kV reference), it is necessary to increase the reactive power input to raise the voltage to 10 kV.

[0067] In step three of the present invention, β represents a deceleration factor, and its value is between (0, 1), which adjusts the length of the voltage correction vector.

[0068] In step four of the present invention, it is judged whether the voltage values of each distributed power source node reach the convergence condition. If so, the iteration is stopped and the calculation ends. If not, the reference voltage and reference frequency are continuously updated for optimization.

[0069] In step four of the present invention, typical values within the preset range adopt strict standards or loose standards, specifically: Voltage amplitude difference: Strict standard: ≤0.001 p.u. (per-unit value); Loose standard: ≤0.01 p.u.

[0070] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0071] The present invention can accurately calculate and analyze the power flow distribution of the power system after the grid connection of distributed power sources, timely discover and prevent potential voltage fluctuations and power imbalance problems, thereby improving the stability of the power system. By real-time monitoring and analyzing the operating state of the power system, the platform can give early warnings of possible fault conditions and provide corresponding countermeasures, effectively preventing the occurrence of large-scale power outages and ensuring the security of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0073] Figure 1 It is a flowchart of the method for analyzing and predicting the power flow of distributed power sources connected to the grid in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0074] The following further describes the present invention in detail in conjunction with the embodiments.

[0075] Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications shall be followed. Those materials or equipment not specified as the manufacturer can be obtained as conventional products through purchase.

[0076] In addition, the described features, structures or characteristics can be combined in any suitable manner in one or more exemplary embodiments. In the following description, many specific details are provided to give a full understanding of the exemplary embodiments of the present disclosure. However, those skilled in the art will realize that one or more of the specific details can be omitted to practice the technical solutions of the present disclosure, or other methods, components, steps, etc. can be adopted. In other cases, well-known structures, methods, implementations or operations are not shown or described in detail to avoid obscuring the various aspects of the present disclosure.

[0077] Embodiment 1

[0078] As Figure 1 shown, a method for analyzing and predicting the power flow of distributed power sources connected to the grid includes the following steps:

[0079] Step 1: Obtain the information of each distributed power generation node according to the grid network topology structure, select a distributed power generation node as the voltage reference node, and initialize the frequency and voltage of each distributed power generation node. Among them, the distributed power generation adopts droop control, and the information of each distributed power generation node includes the active power and reactive power output by the distributed power generation.

[0080] Step 2: Solve the current based on the information of each distributed power generation node.

[0081] Step 3: Solve the voltage based on the information of each distributed power generation node.

[0082] Step 4: Update the reference voltage and reference frequency.

[0083] Step 5: Determine whether the voltage values of each distributed power generation node reach the convergence condition. If so, stop the iteration and the calculation ends; if not, return to Step 2 and continue the iteration.

[0084] Embodiment 2

[0085] As Figure 1 shown, a method for analyzing and predicting the power flow of distributed power generation connected to the grid includes the following steps:

[0086] Step 1: Obtain the information of each distributed power generation node according to the grid network topology structure, select a distributed power generation node as the voltage reference node, and initialize the frequency and voltage of each distributed power generation node. Among them, the distributed power generation adopts droop control, and the information of each distributed power generation node includes the active power and reactive power output by the distributed power generation.

[0087] Step 2: Solve the current based on the information of each distributed power generation node.

[0088] Step 3: Solve the voltage based on the information of each distributed power generation node.

[0089] Step 4: Update the reference voltage and reference frequency.

[0090] Step 5: Determine whether the voltage values of each distributed power generation node reach the convergence condition. If so, stop the iteration and the calculation ends; if not, return to Step 2 and continue the iteration.

[0091] In Step 1, the specific method for initializing the frequency is: synchronize the output frequencies of all distributed power generation nodes with the grid reference frequency.

[0092] In Step 1, the specific method for initializing the voltage is: adjust the voltages of all distributed power generation nodes to within the range of ±5% deviation from the standard voltage.

[0093] In Step 1, the specific method for the distributed power generation to adopt droop control is as follows:

[0094] The droop control model for power flow calculation is as follows:

[0095]

[0096] where m pi and n qi are the droop coefficients of active power - frequency and reactive power - voltage droop control corresponding to the i-th distributed power source respectively, P gi and Q gi are the output active power and output reactive power of the i-th distributed power source respectively, are the reference active power and reference reactive power of the i-th distributed power source respectively, w and w0 are the actual frequency and reference frequency defined at the i-th distributed power source node, |V i | and V0| are the actual voltage amplitude and reference voltage amplitude of the i-th distributed power source node respectively;

[0097] Control is performed using the above-mentioned droop control model.

[0098] The specific method for Step 2 is as follows:

[0099] Calculate the complex power injected into each distributed power source node:

[0100]

[0101] where P li and Q li are the output active load and output reactive load of the i-th distributed power source respectively; S i represents the complex power injected into the i-th distributed power source node;

[0102] Based on the complex power, calculate the current I i of the i-th distributed power source node:

[0103]

[0104] where * represents complex number operation, V i represents the voltage of the i-th distributed power source node;

[0105] From the load node to the reference node, sum up the currents of the distributed power source nodes to calculate the branch current matrix [I ij :

[0106] [I ij = (A T ) -1 [I i ;

[0107] where [I iThe current I of the distributed power source node i The matrix composed of, A is the incidence matrix, A T Is the transpose of the incidence matrix, and the order of the incidence matrix A is N b ×N, where, N b And N respectively represent the number of distributed power source nodes and the number of branch currents;

[0108] The element a in the matrix A ij Is:

[0109] (1) a ij = +1, indicating that the j-th branch is associated with the i-th node, and the branch direction leaves the node i;

[0110] (2) a ij = -1, indicating that the j-th branch is associated with the i-th node, and the branch direction points to the node i;

[0111] (3) a ij = 0, indicating that the j-th branch has no relation with the i-th node.

[0112] The specific method of step three is:

[0113] [V] k+1 =(1 - β)[V] k +β([V REF -(A) -1 diag(Z ij )[I ij )];

[0114] Among them, [V] k+1 Represents the voltage of the (k + 1)-th iteration; [V] k Represents the voltage of the k-th iteration; β represents the deceleration factor; diag(Z ij ) represents the diagonal matrix of branch impedance; [V REF represents the maximum grid-connected voltage of the preset distributed power source.

[0115] The value range of β is (0, 1).

[0116] The specific method of step four is:

[0117] Automatic voltage control AVC system correction:

[0118] The AVC system calculates the voltage control sensitivity matrix by real-time monitoring of the grid voltage and reactive power distribution;

[0119] According to the situation of voltage over-limit nodes, the AVC system corrects the voltage of voltage over-limit nodes in each control area;

[0120] If a certain control area fails to be successfully corrected due to excessive over-limit values or too many over-limit nodes of voltage over-limit nodes, the AVC system will attempt to minimize the voltage over-limit nodes in the entire system through the adjustment of other areas.

[0121] The specific method of Step Four is as follows:

[0122] When the voltage values of each node gradually tend to be stable, that is, the voltage difference between two adjacent iterations is within a preset range, it is determined that the voltage values of each distributed power supply node reach the convergence condition.

[0123] Embodiment 3

[0124] As Figure 1 shown, a method for analyzing and predicting the power flow of distributed power supply grid connection includes the following steps:

[0125] Step One, obtain the information of each distributed power supply node according to the power grid network topology structure, select a distributed power supply node as the voltage reference node, and initialize the frequency and voltage of each distributed power supply node; wherein, the distributed power supply adopts droop control, and the information of each distributed power supply node includes the active power and reactive power output by the distributed power supply.

[0126] Step Two, solve the current based on the information of each distributed power supply node.

[0127] Step Three, solve the voltage based on the information of each distributed power supply node.

[0128] Step Four, update the reference voltage and reference frequency.

[0129] Step Five, determine whether the voltage values of each distributed power supply node reach the convergence condition. If so, stop the iteration and end the calculation; if not, return to Step Two and continue the iteration.

[0130] In summary, the present invention obtains the information of each distributed power supply node according to the power grid network topology structure, selects a distributed power supply node as the voltage reference node, initializes the frequency and voltage of each distributed power supply node, solves the current based on the information of each distributed power supply node; solves the voltage based on the information of each distributed power supply node; updates the reference voltage and reference frequency; determines whether the voltage values of each distributed power supply node reach the convergence condition. The present invention can accurately calculate and analyze the power flow distribution of the power system after the distributed power supply is connected to the grid, timely discover and prevent potential voltage fluctuations and power imbalance problems, thereby improving the stability of the power system. By real-time monitoring and analyzing the operation status of the power system, the platform can early warn possible fault situations and provide corresponding countermeasures, effectively preventing the occurrence of large-scale power outages and ensuring the safety of the power system.

[0131] The droop control of distributed power sources specifically includes the following processes:

[0132] The droop control model for power flow calculation:

[0133]

[0134] Among them, m pi and n qi are respectively the droop coefficients of active power-frequency and reactive power-voltage droop control corresponding to the i-th distributed power source, P gi and Q gi are respectively the output active power and reactive power output of the i-th distributed power source, are respectively the reference active power and reactive power of the i-th distributed power source, w and w0 are respectively the actual frequency and reference frequency defined by the i-th distributed power source node, |V i | and V0| are respectively the actual voltage amplitude and reference voltage amplitude of the i-th distributed power source node.

[0135] Solving for the current based on the information of each distributed power source node specifically includes the following processes:

[0136] Calculate the complex power S injected into each distributed power source node i :

[0137]

[0138] Among them, P li and Q li are respectively the output active load and reactive load of the i-th distributed power source;

[0139] Calculate the current I of the distributed power source node based on the complex power i :

[0140]

[0141] Among them, * represents complex number operation, V i represents the voltage of the distributed power source node;

[0142] From the load node to the reference node, accumulate the currents of the distributed power source nodes to calculate the branch current matrix [I ij :

[0143] [I ij = (A T ) -1 [I i ;

[0144] Among them, [I i represents the current I of the distributed power source node iThe composed matrix, A is the incidence matrix, A T is the transpose of the incidence matrix, and the order of the incidence matrix A is N b ×N, where, N b and N respectively represent the number of distributed power generation nodes and the number of branch currents. The element a ij in matrix A is as follows:

[0145] (1) a ij = +1, indicating that the j-th branch is associated with the i-th node and the branch direction leaves node i;

[0146] (2) a ij = -1, indicating that the j-th branch is associated with the i-th node and the branch direction points to node i;

[0147] (3) a ij = 0, indicating that the j-th branch is not associated with the i-th node.

[0148] Solving the voltage based on the information of each distributed power generation node specifically includes the following process:

[0149] [V] k+1 = (1 - β)[V] k + β([V REF - (A) -1 diag(Z ij )[I ij )];

[0150] Among them, [V] k+1 represents the voltage of the (k + 1)-th iteration, [V] k represents the voltage of the k-th iteration, β represents the deceleration factor, whose value is between (0, 1), and it adjusts the length of the voltage correction vector. diag(Z ij ) represents the diagonal matrix of branch impedance.

[0151] Updating the reference voltage and reference frequency specifically includes the following process:

[0152] Automatic voltage control AVC system correction:

[0153] The AVC system calculates the voltage control sensitivity matrix by real-time monitoring of the distribution of grid voltage and reactive power;

[0154] According to the situation of voltage over-limit nodes, the AVC system corrects the voltage of voltage over-limit nodes in each control area.

[0155] If a certain control area fails to be successfully corrected due to excessive over-limit amount or too many over-limit nodes of voltage over-limit nodes, the AVC system will try to minimize the voltage over-limit nodes of the entire system through the adjustment of other areas.

[0156] Specifically, for the correction of voltage out-of-limit nodes:

[0157] Based on the situation of voltage out-of-limit nodes, the AVC system performs voltage correction on the voltage out-of-limit nodes in each control area. The goal of the correction is to restore the voltage out-of-limit nodes to the set safe range.

[0158] Regional correction strategy:

[0159] If a certain control area fails to correct successfully due to excessive out-of-limit amounts or too many out-of-limit nodes of voltage out-of-limit nodes, the AVC system will not be limited to this area but will try to assist the correction through the adjustment of other areas. This cross-regional adjustment strategy can minimize the voltage out-of-limit nodes of the entire system and improve the voltage stability of the power grid.

[0160] Correction measures and optimization

[0161] Coordination of control devices:

[0162] When performing voltage correction, the AVC system coordinates control devices such as generators and transformers. Usually, the correction is mainly based on generators (because they have reactive power reserves), and the transformer voltage regulation is supplemented. When the generator cannot complete the correction alone, the system will consider using the transformer for auxiliary correction.

[0163] Application of optimization algorithms:

[0164] In addition to the direct voltage correction algorithm, the AVC system may also adopt optimization algorithms such as genetic algorithms for voltage correction. These algorithms can consider more constraint conditions, such as node voltage, branch current, etc., so as to provide a more accurate correction scheme.

[0165] Safety control strategy

[0166] To ensure the safe and stable operation of the power grid, the AVC system will also adopt a series of safety control strategies. For example, the system reactive power reserve strategy can ensure that there is enough reactive power reserve to cope with voltage fluctuations in case of emergencies; the algorithm control strategy can sort control commands, handle problems such as discrete device control delay and action times locking, etc., to ensure the rationality and effectiveness of correction measures.

[0167] Judging whether the voltage values of each distributed power source node reach the convergence condition specifically includes the following process:

[0168] When the voltage values of each node gradually tend to be stable, that is, the voltage difference between two adjacent iterations is within the preset range, it is determined that the voltage values of each distributed power source node reach the convergence condition.

[0169] The above embodiments can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wired (such as infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that contains one or more collections of available media. The available medium can be a magnetic medium (such as a floppy disk, hard disk, magnetic tape), an optical medium (such as a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state drive.

[0170] Those of ordinary skill in the art can realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. A professional technician can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present application.

[0171] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0172] In several embodiments provided in the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only for some logical function divisions, and there can be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of the devices or units can be in electrical, mechanical, or other forms.

[0173] The unit described as a separation component may or may not be physically separated. The component shown as a unit may or may not be a physical unit, that is, it may be located in one place or distributed over multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0174] The method of the present invention is compared with the traditional method, and the results are shown in Table 1.

[0175] Table 1

[0176] Index Traditional droop control This embodiment (after 5 iterations) Maximum voltage deviation (pu) 0.05 0.002 Frequency offset (Hz) 0.2 0.01 Active power distribution error (%) 8％ 1.5％ Reactive power distribution error (%) 10％ 2％ Iterative convergence time (ms) - 15

[0177] According to the results in Table 1 for effect analysis, the decomposition results are as follows:

[0178] (1) Voltage accuracy improvement

[0179] By iteratively correcting the reference voltage, the voltage deviation is reduced from 0.05 pu to 0.002 pu, meeting the IEEE 1547 standard (±0.005 pu).

[0180] (2) Frequency stability enhancement

[0181] The frequency offset is reduced from 0.2 Hz to 0.01 Hz, reducing equipment losses caused by frequency fluctuations.

[0182] (3) Power distribution optimization

[0183] The active / reactive power distribution errors are reduced by 81% and 80% respectively, achieving a more equitable load sharing.

[0184] (4) Convergence speed

[0185] Convergence is achieved within 5 iterations (15 ms), which is suitable for real-time control scenarios.

[0186] Conclusion: In this embodiment, the droop control parameters are optimized through an iterative algorithm, significantly improving the voltage convergence accuracy and stability of the distributed power system. Compared with the traditional droop control, the voltage deviation is reduced by 96%, the frequency offset is reduced by 95%, the power distribution error is reduced by more than 80%, and the convergence time meets the real-time control requirements, making it suitable for scenarios such as microgrids and island operation.

[0187] 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 by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for analyzing and predicting the power flow of distributed power sources connected to the grid, characterized in that, It includes the following steps: Step 1: Obtain the information of each distributed power generation node according to the grid network topology structure, select a distributed power generation node as the voltage reference node, and initialize the frequency and voltage of each distributed power generation node; among them, the distributed power generation adopts droop control, and the information of each distributed power generation node includes the active power and reactive power output by the distributed power generation; Step 2: Solve the current based on the information of each distributed power generation node; Step 3: Solve the voltage based on the information of each distributed power generation node; Step 4: Update the reference voltage and reference frequency; Step 5: Judge whether the voltage values of each distributed power generation node reach the convergence condition. If so, stop the iteration and the calculation ends; if not, return to Step 2 and continue the iteration.

2. The distributed power grid connection power flow analysis and prediction method according to claim 1, characterized in that In Step 1, the specific method for frequency initialization is: Synchronize the output frequencies of all distributed power generation nodes with the grid reference frequency.

3. The distributed power grid connection power flow analysis and prediction method according to claim 1, characterized in that In Step 1, the specific method for voltage initialization is: Adjust the voltages of all distributed power generation nodes to within the range of ±5% deviation from the standard voltage.

4. The distributed power grid-connected power flow analysis and prediction method according to claim 1, characterized in that In Step 1, the specific method for the distributed power generation to adopt droop control is as follows: The droop control model for power flow calculation is as follows: where m pi and n qi are the droop coefficients of the active power - frequency and reactive power - voltage droop controls corresponding to the i-th distributed power source respectively, P gi and Q gi are the output active power and output reactive power of the i-th distributed power source respectively, are the reference active power and reference reactive power of the i-th distributed power source respectively, w and w0 are the actual frequency and reference frequency defined at the i-th distributed power source node, |V i | and |V0| are the actual voltage magnitude and reference voltage magnitude of the i-th distributed power source node respectively; Adopt the described droop control model for control.

5. The distributed power grid-connected power flow analysis and prediction method according to claim 4, characterized in that The specific method for Step 2 is: Calculate the complex power injected into each distributed power generation node: Among them, P li , Q li are respectively the active power load and reactive power load output by the i-th distributed power source; S i represents the complex power injected into the i-th distributed power source node; Calculate the current I of the i-th distributed power source node based on complex power i : where * represents complex operation, and V i represents the voltage of the i-th distributed power generation node; From the load node to the reference node, the currents of the distributed power generation nodes are accumulated to calculate the branch current matrix [I ij : [I ij =(A T ) -1 [I i ; Where, [I i represents the current I of the distributed power generation node i The matrix composed of, A is the incidence matrix, A T Is the transpose of the incidence matrix, and the order of the incidence matrix A is N b ×N, where, N b And N respectively represent the number of distributed power generation nodes and the number of branch currents; The element a in matrix A ij is as follows: (1)a ij = +1, indicating that the j-th branch is associated with the i-th node and the branch direction is away from node i; (2)a ij = -1, indicating that the j-th branch is associated with the i-th node and the branch direction points to node i; (3)a ij = 0, indicating that the j-th branch is independent of the i-th node.

6. The distributed power grid-connected power flow analysis and prediction method according to claim 5, characterized in that The specific method for Step 3 is: [V] k+1 =(1 - β)[V] k +β([V REF - (A) -1 diag(Z ij )[I ij ); Among them, [V] k+1 represents the voltage at the (k + 1)-th iteration; [V] k represents the voltage at the k-th iteration; β represents the deceleration factor; diag(Z ij ) represents the diagonal matrix of the branch impedance; [V REF represents the maximum voltage preset for the grid connection of distributed power sources.

7. The method for analyzing and predicting the grid-connected power flow of distributed power sources according to claim 6, characterized in that, The value range of β is (0, 1).

8. The distributed power grid-connected power flow analysis and prediction method according to claim 1, characterized in that The specific method for Step 4 is: Automatic voltage control AVC system correction: The AVC system calculates the voltage control sensitivity matrix by real-time monitoring of the distribution of grid voltage and reactive power; According to the situation of voltage over-limit nodes, the AVC system corrects the voltage of voltage over-limit nodes in each control area; If a certain control area fails to be successfully corrected due to excessive over-limit amounts or too many over-limit nodes of voltage over-limit nodes, the AVC system will try to minimize the voltage over-limit nodes of the entire system through the adjustment of other areas.

9. The distributed power grid connection power flow analysis and prediction method according to claim 1, characterized in that The specific method for Step 4 is: When the voltage values of each node gradually tend to be stable, that is, the voltage difference between two adjacent iterations is within the preset range, it is determined that the voltage values of each distributed power generation node reach the convergence condition.

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