Method and device for quantitative evaluation of static voltage stability in multi-feed systems

Abstract

This invention discloses a method and apparatus for quantitatively evaluating the static voltage stability of multi-infeed systems, relating to the field of power system online monitoring and control technology. The method constructs power flow mathematical models under different renewable energy grid-connected control strategies and quantitatively evaluates the power transmission capacity and static voltage stability boundary of heterogeneous renewable energy multi-infeed systems under different control and operating modes based on the singularity condition of the power flow Jacobian matrix. It analyzes the influencing factors of static voltage stability from the perspectives of control and system parameters and verifies the effectiveness of the proposed method through simulation.

Description

Technical Field

[0001] This invention discloses a method and apparatus for quantitative evaluation of static voltage stability in multi-infeed systems, relating to the field of power system online monitoring and control technology. Background Technology

[0002] Static voltage stability is a crucial constraint for the stable operation of a power system. With the rapid increase in the proportion of renewable energy sources and the gradual decrease in the proportion of conventional power sources supported by synchronous machines, the static voltage stability margin of the system is continuously declining, posing a severe challenge to the safety and stability of the power system. Most renewable energy power plants use grid-connected converters integrated into the AC grid, exhibiting current-source characteristics. In recent years, grid-connected converters with voltage-source characteristics have been applied in multiple projects due to their supporting role. The coexistence of grid-connected and grid-connected control results in a heterogeneous renewable energy multi-infeed characteristic in the power system. For heterogeneous renewable energy multi-infeed systems, the coupling relationship between voltage stability and control methods, system structure, and other factors is complex. Therefore, revealing the static voltage stability mechanism of heterogeneous renewable energy systems and providing quantitative evaluation methods are crucial for ensuring the safe and stable operation of the power system.

[0003] Currently, there are numerous research findings on the role of grid-based control in enhancing the active support capabilities of renewable energy power plants. However, analysis of mathematical models for grid-based renewable energy power flow is lacking. This makes it crucial to address how to qualitatively and quantitatively analyze the static voltage stability in heterogeneous renewable energy multi-infeed systems, taking into account key characteristic quantities. Existing literature on the static voltage stability of multi-infeed renewable energy systems lacks consideration of constraints from multiple factors such as control and operation modes. Furthermore, there are few studies that quantitatively analyze the grid-connected transmission capacity of heterogeneous renewable energy and the static voltage stability boundary of multi-infeed systems. Current technologies use the minimum singular value of the Jacobian matrix as an indicator to evaluate system static voltage stability and disclose the applicable conditions for the voltage stability margin index of renewable energy transmission systems, but none of these studies consider the impact of renewable energy reactive power and voltage characteristics under different control methods on the evaluation process.

[0004] Therefore, a method and apparatus for quantitative evaluation of static voltage stability in multi-feed systems are invented to solve the above problems. Summary of the Invention

[0005] A method and apparatus for quantitative evaluation of static voltage stability in multi-feed systems are provided, and the technical solution adopted is as follows:

[0006] A first aspect is a method for quantitatively evaluating the static voltage stability of a multi-feed system, the method comprising:

[0007] Step 1: Establish a multi-feed system model;

[0008] Based on the motor power supply, a power flow model is established through a new energy multi-feed-in system;

[0009] Based on the power flow model, a Jacobian matrix is ​​established at the generator node through the new energy multi-feed system;

[0010] Based on the Jacobian matrix, the new energy nodes and the generator nodes are connected to the grid using the power flow model;

[0011] Step 2: Process the new energy nodes according to the control method;

[0012] Based on the type of the new energy node, the corresponding elements of the Jacobian matrix are modified, including:

[0013] When the new energy node is a grid-connected type, the grid-connected unit operates according to the unity power factor and is treated as a PQ node by equivalent current source when connected to the grid.

[0014] Let the active power and reactive power injected into the AC system by the new energy node be P, respectively. S Q S , expressed in complex power form, as shown in formula (8):

[0015]

[0016] Among them, U S δ represents the amplitude of the bus voltage at the PCC grid connection point. S X is the voltage phase angle; T The equivalent reactance of the grid-connected line includes the connecting transformer, while ignoring line resistance and capacitance to ground.

[0017] Setting the reactive power in formula (8) to 0, we obtain the relationship between the grid connection point voltage amplitude, phase angle, and node-injected active power:

[0018] (P S X T ) 2 +U S 4 =U S 2 U g 2 (9)

[0019]

[0020] The effective value of the grid connection point voltage is obtained as follows:

[0021]

[0022] Substituting the above formula (11) into the expression for the elements of the Jacobian matrix, we get:

[0023]

[0024] By modifying the corresponding elements in formula (12) of the Jacobian matrix element expression, we can obtain:

[0025]

[0026] According to the constant voltage control, the grid-connected new energy node is processed into a PV node, which is the same as the generator node; the relationship between the grid connection point voltage amplitude, phase angle and node injected active power is shown in the formula (8). Substituting into the formula (12) of the Jacobian matrix element expression, we have:

[0027]

[0028] Modify the corresponding elements in the Jacobian matrix element expression by changing the elements related to the active power output of the new energy node to:

[0029]

[0030] In the formula:

[0031]

[0032] The elements related to the reactive power output of the new energy node are 0, and the remaining elements are processed as shown in formula (13), thus obtaining the reduced-order Jacobian matrix:

[0033]

[0034] For grid-connected renewable energy nodes, the grid-connected power source exhibits voltage source characteristics under rated operating conditions and is treated as a PV node, and P Si =f(U Si At this point, the modification of the Jacobian matrix elements is as shown in formula (15);

[0035] If the active power output of the grid-connected power source continues to increase or an external circuit fault causes overcurrent, the converter will reach its modulation limit. Once the VSC internal potential reaches its limit, the grid-connected new energy node type will convert to a PQ node, and P... Si =f(U Si ),

[0036] Q Si =f(U Si The elements related to the reactive power output of the new energy node are modified as follows:

[0037]

[0038] Step 3: Quantitatively evaluate the static voltage stability of the multi-feed system;

[0039] Based on the singular values ​​of the Jacobian matrix, the static voltage stability is quantitatively evaluated through the new energy multi-infeed system to obtain the stability boundary of the static voltage.

[0040] In some implementations, in step one, the motor power supply includes asynchronous motor power supplies and traditional synchronous motor power supplies.

[0041] In a second aspect, embodiments of the present invention provide a static voltage stability quantification evaluation device for multi-feed systems, the device comprising:

[0042] The modeling module is used to build models of multi-feed systems, and specifically includes:

[0043] The model unit is used to establish a power flow model based on the motor power supply through a new energy multi-feed system;

[0044] The matrix unit is used to establish a Jacobian matrix at the generator node through the new energy multi-feed system according to the power flow model.

[0045] The node processing unit is used to perform grid connection processing on the new energy nodes and the generator nodes according to the Jacobian matrix and the power flow model;

[0046] The update module is used to process the new energy nodes according to the control method and modify the corresponding elements of the Jacobian matrix according to the type of the new energy nodes.

[0047] The evaluation module is used to quantitatively evaluate the static voltage stability of the multi-infeed system. Based on the matrix singular values ​​of the Jacobian matrix, the static voltage stability of the new energy multi-infeed system is quantitatively evaluated to obtain the stability boundary of the static voltage.

[0048] In some implementations, the motor power supply includes asynchronous motor power supplies and conventional synchronous motor power supplies.

[0049] In some implementations, the new energy nodes include grid-connected new energy nodes and network-structured new energy nodes.

[0050] In some implementations, the update module specifically includes:

[0051] The grid-connected new energy node processing unit is used to process the grid-connected new energy node into a PQ node according to the load model and through the constant impedance model, and to modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-connected new energy node.

[0052] A grid-type new energy node processing unit includes a rated operating subunit and a potential value subunit; wherein, the rated operating subunit is used to process the grid-type new energy node into a PV node when the grid-type power supply is in rated operating state, and modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-type new energy node.

[0053] The potential value sub-unit is used to process the grid-type new energy node into a PQ node when the internal potential of the VSC of the grid-type power source reaches the limit value, and to modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-type new energy node.

[0054] Thirdly, embodiments of the present invention provide an electronic device, including a memory and a processor, wherein the memory is used to store one or more computer instructions, wherein when the one or more computer instructions are executed by the processor, they implement the method described in the first aspect above.

[0055] Fourthly, embodiments of the present invention provide a computer storage medium, wherein a computer program is stored in the computer-readable storage medium, and when the computer program is executed by a processor, it implements the method described in the first aspect.

[0056] One or more embodiments of the present invention can bring at least the following beneficial effects: The method of the present invention constructs a power flow mathematical model under different new energy grid-connected control strategies, and quantitatively evaluates the power output capacity and static voltage stability boundary of heterogeneous new energy multi-infeed system under different control methods and different operating modes based on the singular conditions of the power flow Jacobian matrix. It analyzes the influencing factors of static voltage stability from the aspects of control and system parameters and verifies the effectiveness of the proposed method through simulation. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a simplified topology diagram of a multi-machine feed system provided in an embodiment of the present invention;

[0059] Figure 2 This is a topology diagram of an improved 3-machine 9-node system with multiple machines and single feeder provided in an embodiment of the present invention;

[0060] Figure 3 This is a graph showing the relationship between the power output of each station in a multi-machine single-infeed system and the singularity criterion value of the Jacobian matrix, provided in an embodiment of the present invention.

[0061] Figure 4 This is a graph showing the relationship between the power output of each station in the multi-machine multi-feed system and the singularity criterion value of the Jacobian matrix, provided in an embodiment of the present invention.

[0062] Figure 5 This is a graph showing the relationship between power station output and Jacobian matrix singularity criterion values ​​under different new energy transmission distances provided in this embodiment of the invention.

[0063] Figure 6 This is a graph showing the relationship between the power output of the power station and the singularity criterion value of the Jacobian matrix under different internal potential limiting values ​​provided in the embodiments of the present invention. Detailed Implementation

[0064] It is worth noting that, unless otherwise specified, the methods used in this invention are all conventional methods; and the raw materials and equipment used are all conventional commercially available products, and their sources are not specifically limited.

[0065] Example 1:

[0066] This embodiment provides a method for quantitative evaluation of static voltage stability in multi-feed systems, the method comprising:

[0067] First, following step one, establish a multi-feed system model, which specifically includes:

[0068] S11, Based on the motor power supply, establish a power flow model through a new energy multi-feed system;

[0069] S12, According to the power flow model, a Jacobian matrix is ​​established at the generator node through the new energy multi-feed system;

[0070] S13, Based on the Jacobi matrix, perform grid connection processing on the new energy nodes and the generator nodes through the power flow model;

[0071] The motor power supply includes asynchronous motor power supply and traditional synchronous motor power supply.

[0072] According to S11, assuming a high-proportion renewable energy grid has n nodes, most of which are asynchronous power sources and a small portion are traditional synchronous power sources, the simplified system topology is as follows: Figure 1 As shown.

[0073] The injected power at node i is represented by P. Si Q Si The load of node i is represented by P. Li Q Li If we express this as an expression, then the power balance equation for the i-th node of the power grid is as follows:

[0074]

[0075] In the formula ΔP i ΔQ i These represent the active and reactive power imbalances at node i, respectively; U i U j Let G be the voltage magnitudes at nodes i and j, respectively; ij B ij These represent the conductance and susceptance between nodes i and j, respectively; δ ij Let be the phase angle difference between nodes i and j.

[0076] According to S12, synchronous generator nodes are usually treated as slack nodes or PV nodes, and the load model adopts the constant impedance (ZIP) model, which is usually treated as a PQ node. Thus, the Jacobian matrix on the AC side is obtained as follows:

[0077]

[0078] The Jacobian matrix of a new energy multi-infeed system includes the Jacobian matrix J on the AC system side. ac And the equipment-side Jacobian matrix J S Based on the power flow model of a multi-feed system, it can be expanded as follows:

[0079]

[0080] Among them, J ac It includes all generators, loads, and their interconnection nodes in the AC system, J S It includes all new energy nodes and the grid-connected nodes on the AC system side connected to them. According to Figure 1 According to S13, the Jacobian matrix element expression corresponding to the new energy node is:

[0081]

[0082]

[0083] In the formula, node i is the grid connection point of the equipment, and node j is the AC system side node connected to the equipment.

[0084] For asynchronous power nodes, the power injected into the AC system includes information such as controller parameters. Next, we will consider different types of new energy nodes and modify the elements in the corresponding Jacobian matrix.

[0085] The next step is to process the new energy nodes according to step two and the control method.

[0086] Based on the type of the new energy node, the corresponding elements of the Jacobian matrix are modified; wherein, the new energy node includes a follow-mesh type new energy node and a network-structure type new energy node, specifically including:

[0087] S21. Based on the load model, the grid-connected new energy node is processed into a PQ node through the constant impedance model, and the corresponding elements of the Jacobian matrix are modified to obtain the element expression of the grid-connected new energy node.

[0088] S22, When the grid-type power supply is in its rated operating state, the grid-type new energy node is processed into a PV node, and the corresponding elements of the Jacobian matrix are modified to obtain the element expression of the grid-type new energy node.

[0089] S23, when the VSC internal potential of the grid-connected power source reaches the limit value, the grid-connected new energy node is processed into a PQ node, and the corresponding elements of the Jacobian matrix are modified to obtain the element expression of the grid-connected new energy node.

[0090] For grid-connected renewable energy nodes, the grid-connected units operate primarily at unity power factor. During grid connection, they are treated as current sources, specifically PQ nodes. Let the active and reactive power injected into the AC system by the renewable energy node be PQ and PQ, respectively. S Q S U is expressed in complex power form; S δ represents the amplitude of the bus voltage at the PCC grid connection point. S X is the voltage phase angle; T The equivalent reactance of the grid-connected line includes the connecting transformer, while neglecting line resistance and ground capacitance. Its output active and reactive power are:

[0091]

[0092] Setting the reactive power to 0 in the above equation, we obtain the relationship between the grid connection point voltage amplitude, phase angle, and node-injected active power:

[0093] (P S X T ) 2 +U S 4 =U S 2 U g 2 (9)

[0094]

[0095] The effective value of the grid connection point voltage is obtained as follows:

[0096]

[0097] Substituting equation (11) into the expression for the elements of the Jacobian matrix, we get:

[0098]

[0099] By modifying the corresponding elements in the Jacobian matrix, we can obtain:

[0100]

[0101] The grid-connected new energy node under constant voltage control is treated as a PV node, the same as the generator node. The relationship between the grid connection point voltage amplitude, phase angle and node injected active power is the same as in equation (8). Substituting into the Jacobian matrix element expression, we have:

[0102]

[0103] When modifying the corresponding elements in the Jacobian matrix, only the elements related to the active power output of the new energy nodes need to be modified as follows:

[0104]

[0105] In the formula:

[0106]

[0107] The elements related to the reactive power output of the new energy node are 0, and the processing of the remaining elements is the same as in equation (13), thus obtaining the reduced Jacobian matrix.

[0108]

[0109] For grid-connected renewable energy nodes, the grid-connected power source exhibits voltage source characteristics under rated operating conditions and is treated as a PV node, and P Si =f(U Si At this point, the modification of the Jacobian matrix elements is the same as in equation (15).

[0110] If the active power output of the grid-connected power source continues to increase or an external circuit fault causes overcurrent, the converter will reach its modulation limit. Once the VSC internal potential reaches its limit, the grid-connected new energy node type will convert to a PQ node, and P... Si =f(U Si ),

[0111] Q Si =f(U Si The elements related to the reactive power output of new energy nodes have been modified as follows:

[0112]

[0113] The processing of the remaining elements is the same as in equation (15). Thus, the element expressions of the new energy node part in the power flow Jacobian matrix of the multi-feed system under different control modes are obtained.

[0114] The next step is to conduct a quantitative assessment of the static voltage stability of the multi-infeed system, following step three.

[0115] Based on the singular values ​​of the Jacobian matrix, the static voltage stability is quantitatively evaluated through the new energy multi-infeed system to obtain the stability boundary of the static voltage.

[0116] Step two yielded the system power flow Jacobian matrix form under different renewable energy control methods. The main diagonal and off-diagonal elements directly related to the renewable energy grid connection point include the transmission power P. Si Q Si Node voltage V Ti δ Si Information such as the main diagonal elements of the system power flow Jacobian matrix. The Jacobian matrix represents the self-feedback term in the system, reflecting the system's power balance and transmission capacity. Since the necessary and sufficient condition for a matrix to be singular is that it is a dangling matrix, that is, the sum of its diagonal and off-diagonal elements is zero, if the off-diagonal elements are close to the diagonal elements, the matrix may exhibit linear dependence, which in turn leads to the Jacobian matrix having a singular value of zero or close to zero, indicating that the matrix may be singular, and at this time the system is close to an unstable state.

[0117] In a multi-machine single-feed scenario, in J S The matrix block corresponding to the voltage phase angle and amplitude information of the AC system side node and this node is J1; the matrix block corresponding to the AC system side node and the new energy node information is J2; the matrix block corresponding to the new energy node and the AC system side node information is J3; and the matrix block corresponding to the new energy node's own information is J4. Taking the Jacobian matrix of the external equipment side of the grid-connected power supply as an example:

[0118]

[0119] The general expression for the Jacobian matrix on the external equipment side of a multi-machine single-feed system is:

[0120]

[0121] Where i and j represent different renewable energy power stations. Furthermore, J2 and J3 satisfy J2 = J3. T That is, for a multi-generator single-infeed renewable energy system, its Jacobian matrix remains a symmetric matrix. The main diagonal elements directly related to the renewable energy output power and grid connection voltage are... The non-diagonal elements are max{P Si ,P Sj}, thus obtaining the simplified condition that the system's power flow Jacobian matrix is ​​close to singular:

[0122]

[0123] For multi-unit single-infeed renewable energy systems, the close electrical distance between power stations creates node voltage and power coupling relationships, which may limit their renewable energy transmission capacity. The following analysis will focus on multi-unit multi-infeed systems.

[0124] In multi-machine, multi-feed scenarios, the following steps will be followed: Figure 1 The multi-machine multi-feed system shown is analyzed. By analogy with equation (20), the general expression for the Jacobian matrix of the external equipment side of the multi-machine multi-feed system is derived as follows:

[0125]

[0126] According to the general properties of the power flow Jacobian matrix in an AC system, J ij and J ji Satisfy J ij =J ji T Therefore, the top-left Jacobian matrix block of the autocorrelation of the AC system is a symmetric matrix, and the bottom-right Jacobian matrix block of the autocorrelation of the new energy node is a diagonal matrix. Considering the characteristics of the external equipment side, the singularity condition of the system's Jacobian matrix is ​​as follows:

[0127] min{|J 4i |,|J 4j |}→0 (23)

[0128] Equation (23) is essentially a simplified generalization of Equation (21), and its external device side can be equivalent to a power supply sent from a single point.

[0129] The critical points discussed here refer to the operating boundary when the system reaches the static voltage stability limit. In reality, renewable energy units with a certain low-voltage ride-through capability experience a rapid decrease in active power output during the low-voltage ride-through state. After the low-voltage ride-through state ends, the active power output recovers slowly, and the system operates within the static stability limit boundary. Units without low-voltage ride-through capability will trip when the voltage drops below 0.9 pu, also operating within the static stability limit boundary. Furthermore, in actual systems, the system power flow may become non-convergent before the Jacobian matrix on the external equipment side reaches the singular condition. Taking a load node near the renewable energy feed-in point as an example, its nonlinear equation is:

[0130]

[0131] Where P W Q W To inject power into load nodes from new energy sources, P L Q LGiven the active and reactive power parameters of the load, it can be seen that the self-feedback term of the load node is affected by the power transmitted by the external equipment. In a multi-machine multi-infeed system, the number of nodes connected to new energy sources increases, and the parameter information in equation (24) will be incorporated into the Jacobian matrix on the external equipment side, which increases the matrix order dimension described in equation (22) and increases the complexity of singularity analysis. In order to obtain the relationship between the power flow convergence and the degree of new energy penetration in a multi-machine multi-infeed system, the load node voltage sensitivity is introduced to indicate the voltage response of the point when the external equipment changes. In the multi-machine multi-infeed scenario, the voltage sensitivity distribution range of each load node is large, indicating that the nodes in the system are more susceptible to the influence of external equipment power fluctuations, and the system has already reached the critical state before the singularity criterion tends to 0.

[0132] Because changes in the power and voltage of nodes related to the Jacobian matrix on the external equipment side will cause changes in the overall AC system, voltage-weak nodes (such as heavily loaded nodes) in the system will first drop to a voltage collapse state, causing the system to become unstable before the Jacobian matrix becomes singular. This characteristic will be more pronounced in multi-machine multi-infeed systems with high renewable energy penetration. Therefore, the stability boundary calculated by the method proposed in this patent is more conservative than that under actual operating conditions and has wider applicability.

[0133] Example 2:

[0134] Based on Example 1, the new energy transmission capability of the multi-infeed system is verified:

[0135] This example is based on an improved 3-machine system, replacing generator G3 with a new energy power station that includes grid-connected and grid-connected control, such as... Figure 2 As shown, the power transmission distance of the new energy power station is set to 100km.

[0136] The power plant output was increased, and multiple simulations were performed to derive the relationship between the new energy output and the changes in the main and secondary diagonal elements of the Jacobian matrix on the external equipment side, as follows: Figure 3 As shown, with the increase of power plant output, the voltage associated with the new energy node drops significantly until the system becomes unstable. The main diagonal element continues to decrease, and the maximum power output is 4.8 pu when it approaches the maximum value of the secondary diagonal element. If the same experiment is performed on a power plant with only grid-connected new energy, the grid connection point voltage will continue to decrease with the increase of power plant output. The maximum power output corresponding to the system instability is 3.52 pu, which verifies the effectiveness of the method in step three.

[0137] Analysis of the power output of various configurations of the power station under the multi-machine single-infeed scenario and the results of the Jacobian matrix singularity criterion shows that when the system reaches the critical point, its Jacobian matrix approaches singularity and does not fully satisfy the singularity condition. That is, the main diagonal elements are still slightly larger than the secondary diagonal elements. This also proves that, as proposed in step three, there is a complex coupling mechanism between the new energy source and the AC system in actual operation, which may cause the system to become unstable before reaching the static voltage stability critical point.

[0138] The three-machine, nine-node system was further modified by distributing heterogeneous new energy power stations into nodes 5 and 9 of the system. While keeping the system parameters unchanged, the above theoretical analysis was simulated and verified based on the multi-machine, multi-feed system to simulate the distributed grid connection scenario of new energy.

[0139] Similarly, by setting up an increase in power output at the power station and conducting multiple sets of experiments, the relationship between the total power output and the determinant of the Jacobian matrix on the external equipment side was obtained as follows: Figure 4 As shown, the minimum singular value of the Jacobian matrix is ​​introduced as an auxiliary criterion. In a distributed grid-connected scenario, as the power plant output continuously increases, the voltage associated with the renewable energy nodes begins to decrease, the determinant of the Jacobian matrix decreases, and the minimum singular value approaches 0, resulting in a renewable energy limit output of 5.04 pu. If the same experiment is conducted in a power plant with only grid-connected renewable energy, the limit power output corresponding to system instability is 3.62 pu, which also verifies the effectiveness of the method in step three.

[0140] However, in distributed grid-connected scenarios, the difference in the singularity criterion of the Jacobian matrix on the external device side when voltage instability occurs will be larger. This also verifies that, as proposed in step three, in multi-machine multi-infeed systems with high renewable energy penetration, the impact of renewable energy on the grid-connected system will be more significant, and the system is more likely to become unstable before reaching the static voltage stability critical point.

[0141] Simulation verification of influencing factors was conducted based on a heterogeneous new energy multi-infeed system.

[0142] Keeping other system parameters unchanged, the transmission distances were set to 100km, 130km, and 160km, respectively, and the corresponding line impedances X were determined. T For values ​​of 0.06 pu, 0.08 pu, and 0.10 pu, the relationship between the total power output of the power station and the determinant of the Jacobian matrix on the external equipment side is obtained as follows: Figure 5 As shown.

[0143] Simulation results show that as the transmission distance increases, the power output limit of the station continuously decreases, indicating that the method proposed in this patent still has good applicability under different system structures.

[0144] Based on the influence of the modulation parameters of the grid-type power controller, keeping other system parameters constant, the Vq limiting values ​​are set to 1.00pu, 1.25pu, and 1.50pu respectively. The relationship between the total power output of the power station and the determinant of the Jacobian matrix on the external equipment side is obtained as follows: Figure 6 As shown.

[0145] Simulation results show that increasing the upper limit of the controller modulation stage can improve the power output limit of the new energy power station to a certain extent. The static stability limit point shifts to the left as the control parameters increase, which also verifies that the method proposed in this patent still has good applicability under different new energy controller parameters.

[0146] Example 3:

[0147] This invention provides a device for quantitatively evaluating the static voltage stability of a multi-feed system, the device comprising:

[0148] The modeling module is used to build models of multi-feed systems, and specifically includes:

[0149] The model unit is used to establish a power flow model based on the motor power supply through a new energy multi-feed system;

[0150] The matrix unit is used to establish a Jacobian matrix at the generator node through the new energy multi-feed system according to the power flow model.

[0151] The node processing unit is used to perform grid connection processing on the new energy nodes and the generator nodes according to the Jacobian matrix and the power flow model;

[0152] The update module is used to process the new energy nodes according to the control method and modify the corresponding elements of the Jacobian matrix according to the type of the new energy nodes.

[0153] The evaluation module is used to quantitatively evaluate the static voltage stability of the multi-infeed system. Based on the matrix singular values ​​of the Jacobian matrix, the static voltage stability of the new energy multi-infeed system is quantitatively evaluated to obtain the stability boundary of the static voltage.

[0154] Specifically, the motor power supply includes asynchronous motor power supply and traditional synchronous motor power supply.

[0155] Specifically, the new energy nodes include grid-connected new energy nodes and network-structured new energy nodes.

[0156] Specifically, the update module includes:

[0157] The grid-connected new energy node processing unit is used to process the grid-connected new energy node into a PQ node according to the load model and through the constant impedance model, and to modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-connected new energy node.

[0158] A grid-type new energy node processing unit includes a rated operating subunit and a potential value subunit; wherein, the rated operating subunit is used to process the grid-type new energy node into a PV node when the grid-type power supply is in rated operating state, and modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-type new energy node.

[0159] The potential value sub-unit is used to process the grid-type new energy node into a PQ node when the internal potential of the VSC of the grid-type power source reaches the limit value, and to modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-type new energy node.

[0160] Example 4:

[0161] This embodiment also provides an electronic device, including a memory and a processor, wherein the memory is used to store one or more computer instructions, wherein the one or more computer instructions are executed by the processor to implement the method of Embodiment 1;

[0162] In practical applications, the processor can be implemented as an Application Specific Integrated Circuit (ASIC), Digital Signal Processor (DSP), Digital Signal Processing Device (DSPD), Programmable Logic Device (PLD), Field Programmable Gate Array (FPGA), controller, microcontroller unit (MCU), microprocessor, or other electronic components to execute the methods described in the above embodiments.

[0163] The method implemented in this embodiment is as described in Embodiment 1.

[0164] Example 5:

[0165] This embodiment also provides a computer storage medium, in which a computer program is stored, and when the computer program is executed by one or more processors, it implements the method of embodiment one.

[0166] The computer-readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0167] The method implemented in this embodiment is as described in Embodiment 1.

[0168] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for quantitatively evaluating the static voltage stability of multi-infeed systems, characterized in that, The method includes: Step 1: Establish a multi-feed system model; Based on the motor power supply, a power flow model is established through a new energy multi-feed-in system; Based on the power flow model, a Jacobian matrix is ​​established at the generator node through the new energy multi-feed system; Based on the Jacobian matrix, the new energy nodes and the generator nodes are connected to the grid using the power flow model; Step 2: Process the new energy nodes according to the control method; Based on the type of the new energy node, the corresponding elements of the Jacobian matrix are modified, including: When the new energy node is a grid-connected type, the grid-connected unit operates according to the unity power factor and is treated as a PQ node by equivalent current source when connected to the grid. Let the active power and reactive power injected into the AC system by the new energy node be P, respectively. S Q S , expressed in complex power form, as shown in formula (8): Among them, U S δ represents the amplitude of the bus voltage at the PCC grid connection point. S X is the voltage phase angle; T The equivalent reactance of the grid-connected line includes the connecting transformer, while ignoring line resistance and capacitance to ground. Setting the reactive power in formula (8) to 0, we obtain the relationship between the grid connection point voltage amplitude, phase angle, and node-injected active power: (P S X T ) 2 +U S 4 =U S 2 U g 2 (9) The effective value of the grid connection point voltage is obtained as follows: Substituting the above formula (11) into the expression for the elements of the Jacobian matrix, we get: By modifying the corresponding elements in formula (12) of the Jacobian matrix element expression, we can obtain: The grid-connected new energy node under constant voltage control is treated as a PV node, the same as the generator node; the relationship between the voltage amplitude, phase angle and active power injected into the node at the grid connection point is shown in the above formula (8). Substituting into the formula (12) of the Jacobian matrix element expression, we have: Modify the corresponding elements in the Jacobian matrix element expression by changing the elements related to the active power output of the new energy node to: Where: The elements related to the reactive power output of the new energy node are 0, and the remaining elements are processed as shown in formula (13), thus obtaining the reduced-order Jacobian matrix: For grid-connected renewable energy nodes, the grid-connected power source exhibits voltage source characteristics under rated operating conditions and is treated as a PV node, and P Si =f(U Si At this point, the modification of the Jacobian matrix elements is as shown in formula (15); If the active power output of the grid-connected power source continues to increase or an external circuit fault causes overcurrent, the converter will reach its modulation limit. Once the VSC internal potential reaches its limit, the grid-connected new energy node type will convert to a PQ node, and P... Si =f(U Si ), Q Si =f(U Si The elements related to the reactive power output of the new energy node are modified as follows: Step 3: Quantitatively evaluate the static voltage stability of the multi-feed system; Based on the singular values ​​of the Jacobian matrix, the static voltage stability is quantitatively evaluated through the new energy multi-infeed system to obtain the stability boundary of the static voltage.

2. The method according to claim 1, characterized in that, In step one, the motor power supply includes asynchronous motor power supply and traditional synchronous motor power supply.

3. A device for quantitatively evaluating the static voltage stability of multi-feed systems. The method according to claim 1 is characterized in that, The device includes: The modeling module is used to build models of multi-feed systems, and specifically includes: The model unit is used to establish a power flow model based on the motor power supply through a new energy multi-feed system; The matrix unit is used to establish a Jacobian matrix at the generator node through the new energy multi-feed system according to the power flow model. The node processing unit is used to perform grid connection processing on the new energy nodes and the generator nodes according to the Jacobian matrix and the power flow model; The update module is used to process the new energy nodes according to the control method and modify the corresponding elements of the Jacobian matrix according to the type of the new energy nodes. The evaluation module is used to quantitatively evaluate the static voltage stability of the multi-infeed system. Based on the matrix singular values ​​of the Jacobian matrix, the static voltage stability of the new energy multi-infeed system is quantitatively evaluated to obtain the stability boundary of the static voltage.

4. The apparatus according to claim 3, characterized in that, The motor power supply includes asynchronous motor power supply and traditional synchronous motor power supply.

5. The apparatus according to claim 4, characterized in that, The new energy nodes include grid-connected new energy nodes and network-structured new energy nodes.

6. The apparatus according to claim 5, characterized in that, The update module specifically includes: The grid-connected new energy node processing unit is used to process the grid-connected new energy node into a PQ node according to the load model and through the constant impedance model, and to modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-connected new energy node. A grid-type new energy node processing unit includes a rated operating subunit and a potential value subunit; wherein, the rated operating subunit is used to process the grid-type new energy node into a PV node when the grid-type power supply is in rated operating state, and modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-type new energy node. The potential value sub-unit is used to process the grid-type new energy node into a PQ node when the internal potential of the VSC of the grid-type power source reaches the limit value, and to modify the corresponding elements of the Jacobian matrix to obtain the element expression of the grid-type new energy node.

7. An electronic device, characterized in that, The system includes a memory and a processor, the memory being used to store one or more computer instructions, wherein the one or more computer instructions, when executed by the processor, implement the method as described in claim 1 or 2 above.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium contains a computer program that, when executed by a processor, is used to implement the method as described in claim 1 or 2 above.

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