A method and system for determining electromagnetic transient small signal stability of a power system

Abstract

The application discloses a kind of method and system for determining the electromagnetic transient small signal stability of power system, belong to power system simulation and analysis technical field.The method of the present application comprises: for the power system to be analyzed, the state model and algebraic model of the power supply in the power system are established;Determine the power supply type of each bus in the power system, according to the power supply type of each bus and the state model and algebraic model of the power supply, a coordinate transformation model is constructed;The power grid transmission line of the power system is π type equivalent, and a branch model is established;Based on the coordinate transformation model and the branch model, the Jacobian matrix of the power system is constructed, and the eigenvalue of the Jacobian matrix is obtained, and based on the eigenvalue, the electromagnetic transient small signal stability of the power system is determined.The present application can establish the Jacobian matrix of the whole system electromagnetic transient, and the eigenvalue is solved, to realize the frequency domain analysis and calculation of various broadband oscillation modes.

Description

Technical Field

[0001] This invention relates to the field of power system simulation and analysis technology, and more specifically, to a method and system for determining the electromagnetic transient small disturbance stability of a power system. Background Technology

[0002] To accelerate the achievement of the "carbon peak and carbon neutrality" goals, my country's renewable energy power generation scale has expanded rapidly in recent years. With the accelerated grid connection of renewable energy sources, the stability issues of systems dominated by converter power sources, such as wind and photovoltaic power generation, differ from those of traditional synchronous generator-based systems. The connection of a large number of renewable energy power generation systems to weak systems can lead to various oscillation problems.

[0003] Practical engineering shows that with the integration of high-proportion converter power supplies, traditional grid stability problems become increasingly prominent, and new stability problems also emerge, which are the main constraints limiting the large-scale transmission of new energy. Currently, although there are many methods to effectively analyze small disturbances occurring in high-proportion converter power supplies under electromagnetic transients, each has its own limitations.

[0004] Traditional analysis of small-disturbance stability in power systems primarily relies on electromechanical transients, rarely utilizing electromagnetic transient analysis. Electromechanical transient models only consider the characteristics of components at the power frequency, such as applying π-type equivalents to transmission lines and "connecting" power sources based on the system's node-admittance matrix. While electromechanical transient analysis has made significant progress in analyzing low-frequency oscillations, its limitation to power frequency models and neglect of other frequency bands prevents extended analysis in broadband oscillation domains.

[0005] The small-disturbance stability analysis of electromagnetic transients in power systems aims to achieve analysis of various oscillation modes over a wide frequency band, thus differing from electromechanical transient analysis in its model establishment. From an electromagnetic transient perspective, the power grid portion cannot rely solely on admittance equations; it requires establishing differential equations for line inductance and ground capacitance. Similarly, the internal control of converters necessitates establishing differential-algebraic equations for each control element. These differences in model and equation establishment clearly demonstrate the distinction between electromechanical and electromagnetic transients.

[0006] Therefore, there is an urgent need to establish new methods that can be used to analyze the electromagnetic transients of power systems.

[0007] State-space analysis is a class of analytical methods that constructs a state space based on the system's differential-algebraic equations and analyzes the system matrix. It utilizes Lyapunov's stability theorem and combines matrix eigenvalue calculations to determine stability. This method is characterized by its comprehensive analysis of factors and consideration of the dynamics of each component. However, current literature primarily focuses on modeling single-machine infinite bus systems, with no reports on its application in multi-machine systems.

[0008] Impedance analysis is a widely used method for analyzing broadband oscillations. Its core lies in constructing equivalent impedance models for both the power source and the grid, and then using the Nyquist criterion to analyze the gain and phase margins from a frequency domain perspective, thereby determining system stability. While this method is widely used in engineering, it still has certain limitations in explaining the underlying mechanisms. Summary of the Invention

[0009] To address the above problems, this invention proposes a method for determining the electromagnetic transient small-disturbance stability of a power system, comprising:

[0010] For the power system to be analyzed, a state model and an algebraic model of the power sources in the power system are established;

[0011] Determine the power source type of each bus in the power system, and construct a coordinate transformation model based on the power source type, state model, and algebraic model of each bus.

[0012] The power grid transmission lines of the power system are subjected to π-type equivalent modeling to establish a branch model;

[0013] Based on the coordinate transformation model and branch model, the Jacobian matrix of the power system is constructed, and the eigenvalues ​​of the Jacobian matrix are obtained. Based on the eigenvalues, the electromagnetic transient small disturbance stability of the power system is determined.

[0014] Optional power supply types include: synchronous type and grid-connected converter type.

[0015] Optionally, if the power supply type is a synchronous machine, the constructed coordinate transformation model includes: a synchronous machine current coordinate transformation model and a synchronous machine voltage coordinate transformation model.

[0016] Optionally, the formula for the synchronous machine current coordinate transformation model is as follows:

[0017]

[0018]

[0019] in, The output current of the d-axis of the synchronous motor connected to bus i is... The output current of the q-axis of the synchronous motor connected to bus i is... δ represents the x-axis component of the output current of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. The x-axis component of the output current of the synchronous machine connected to bus i.

[0020] Optionally, the formula for the synchronous machine voltage coordinate transformation model is as follows:

[0021]

[0022]

[0023] in, Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. δ is the voltage at the d-axis terminal of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. This is the voltage at the q-axis of the synchronous machine connected to bus i.

[0024] Optionally, if the power supply type is a grid-connected converter, the constructed coordinate transformation model includes: a grid-connected converter current coordinate transformation model and a grid-connected converter voltage coordinate transformation model.

[0025] Optionally, the formula for the current coordinate transformation model of the grid converter is as follows:

[0026]

[0027]

[0028] in, This refers to the d-axis output current connected to bus i and the grid converter. Let θ be the x-axis component of the output current connected to bus i and the grid converter. i0 The initial phase angle of the grid converter connected to bus i is given. The y-axis component of the output current connected to bus i and the grid converter. This refers to the q-axis output current connected to bus i and the grid converter.

[0029] Optionally, the formula for the voltage coordinate transformation model of the grid converter is as follows:

[0030]

[0031]

[0032] in, For the voltage component on the x-axis at the point of connection between bus i and the grid-connected converter, Let θ be the d-axis voltage value connected to the grid connection point of the grid-connected converter at bus i. i0 The initial phase angle of the grid converter connected to bus i is given. This represents the q-axis voltage value at the connection point between bus i and the grid-connected converter. The x-axis component represents the voltage at the grid connection point of the grid-connected converter connected to bus i.

[0033] Optional branch models include: series branch models for connecting two buses and parallel branch models for buses to ground.

[0034] Alternatively, the formula for the series branch model is as follows:

[0035]

[0036] in, Let d be the d-axis component of the first derivative of the current flowing from bus A to bus B with respect to time. Z represents the q-axis component of the first time derivative of the current flowing from bus A to bus B. B The impedance reference value is given under rated voltage and rated power, where L is the inductance of the line, and u is the impedance reference value. Ad Let u be the d-axis component of the voltage at bus A. Aq Let u be the q-axis component of the voltage at bus A. Bd Let u be the d-axis component of the voltage at bus B. Bq Let ω be the q-axis component of the voltage at bus B, R be the resistance of the line, and ω be the q-axis component of the voltage at bus B. B This is the reference value for the system's angular frequency.

[0037] Optionally, the formula for the parallel branch model is as follows:

[0038]

[0039] in, Let be the d-axis component of the first derivative of the bus voltage with respect to time. Let i be the q-axis component of the first derivative of the bus voltage with respect to time. fd i is the d-axis component of the current flowing into the equivalent ground capacitance. fq For the q-axis component of the current flowing into the equivalent capacitance to ground, C f Z is the capacitance value of the equivalent capacitance to ground. B The impedance reference value under rated voltage and rated power, ω B u is the reference value for the system's angular frequency. q U is the q-axis component of the bus voltage. d Let be the d-axis component.

[0040] Furthermore, this invention also proposes a system for determining the electromagnetic transient small-disturbance stability of a power system, comprising:

[0041] The first model building module is used to establish the state model and algebraic model of the power sources in the power system to be analyzed.

[0042] The second model building module determines the power supply type of each bus in the power system and constructs a coordinate transformation model based on the power supply type, state model and algebraic model of each bus.

[0043] The third model building module is used to perform π-type equivalent transformation on the power grid transmission lines of the power system and establish branch models.

[0044] The output module is used to construct the Jacobian matrix of the power system based on the coordinate transformation model and the branch model, obtain the eigenvalues ​​of the Jacobian matrix, and determine the electromagnetic transient small disturbance stability of the power system based on the eigenvalues.

[0045] Optional power supply types include: synchronous type and grid-connected converter type.

[0046] Optionally, if the power supply type is a synchronous machine, the constructed coordinate transformation model includes: a synchronous machine current coordinate transformation model and a synchronous machine voltage coordinate transformation model.

[0047] Optionally, the formula for the synchronous machine current coordinate transformation model is as follows:

[0048]

[0049]

[0050] in, The output current of the d-axis of the synchronous motor connected to bus i is... The output current of the q-axis of the synchronous motor connected to bus i is... δ represents the x-axis component of the output current of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. The x-axis component of the output current of the synchronous machine connected to bus i.

[0051] Optionally, the formula for the synchronous machine voltage coordinate transformation model is as follows:

[0052]

[0053]

[0054] in, Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. δ is the voltage at the d-axis terminal of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. This is the voltage at the q-axis of the synchronous machine connected to bus i.

[0055] Optionally, if the power supply type is a grid-connected converter, the constructed coordinate transformation model includes: a grid-connected converter current coordinate transformation model and a grid-connected converter voltage coordinate transformation model.

[0056] Optionally, the formula for the current coordinate transformation model of the grid converter is as follows:

[0057]

[0058]

[0059] in, This refers to the d-axis output current connected to bus i and the grid converter. Let θ be the x-axis component of the output current connected to bus i and the grid converter. i0 The initial phase angle of the grid converter connected to bus i is given. The y-axis component of the output current connected to bus i and the grid converter. This refers to the q-axis output current connected to bus i and the grid converter.

[0060] Optionally, the formula for the voltage coordinate transformation model of the grid converter is as follows:

[0061]

[0062]

[0063] in, For the voltage component on the x-axis at the point of connection between bus i and the grid-connected converter, Let θ be the d-axis voltage value connected to the grid connection point of the grid-connected converter at bus i. i0 The initial phase angle of the grid converter connected to bus i is given. This represents the q-axis voltage value at the connection point between bus i and the grid-connected converter. The x-axis component represents the voltage at the grid connection point of the grid-connected converter connected to bus i.

[0064] Optional branch models include: series branch models for connecting two buses and parallel branch models for buses to ground.

[0065] Alternatively, the formula for the series branch model is as follows:

[0066]

[0067] in, Let d be the d-axis component of the first derivative of the current flowing from bus A to bus B with respect to time. Z represents the q-axis component of the first time derivative of the current flowing from bus A to bus B. BThe impedance reference value is given under rated voltage and rated power, where L is the inductance of the line, and u is the impedance reference value. Ad Let u be the d-axis component of the voltage at bus A. Aq Let u be the q-axis component of the voltage at bus A. Bd Let u be the d-axis component of the voltage at bus B. Bq Let ω be the q-axis component of the voltage at bus B, R be the resistance of the line, and ω be the q-axis component of the voltage at bus B. B This is the reference value for the system's angular frequency.

[0068] Optionally, the formula for the parallel branch model is as follows:

[0069]

[0070] in, Let be the d-axis component of the first derivative of the bus voltage with respect to time. Let i be the q-axis component of the first derivative of the bus voltage with respect to time. fd i is the d-axis component of the current flowing into the equivalent ground capacitance. fq For the q-axis component of the current flowing into the equivalent capacitance to ground, C f Z is the capacitance value of the equivalent capacitance to ground. B The impedance reference value under rated voltage and rated power, ω B u is the reference value for the system's angular frequency. q U is the q-axis component of the bus voltage. d Let be the d-axis component.

[0071] In another aspect, the present invention also provides a computing device, comprising: one or more processors;

[0072] A processor is used to execute one or more programs;

[0073] When the one or more programs are executed by the one or more processors, the method described above is implemented.

[0074] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method described above.

[0075] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0076] This invention proposes a method for determining the electromagnetic transient small-disturbance stability of a power system, comprising: establishing a state model and an algebraic model of the power sources in the power system to be analyzed; determining the power source type of each bus in the power system; constructing a coordinate transformation model based on the power source type and the state and algebraic models of the power sources; performing π-type equivalent transformation on the power grid transmission lines of the power system to establish a branch model; constructing the Jacobian matrix of the power system based on the coordinate transformation model and the branch model, obtaining the eigenvalues ​​of the Jacobian matrix, and determining the electromagnetic transient small-disturbance stability of the power system based on the eigenvalues. This invention can achieve frequency domain analysis and calculation of various broadband oscillation modes by establishing the Jacobian matrix of the electromagnetic transients of the entire system and obtaining the eigenvalues. Attached Figure Description

[0077] Figure 1 This is a flowchart of the method of the present invention;

[0078] Figure 2 This is a flowchart of an embodiment of the method of the present invention;

[0079] Figure 3 This is a typical system wiring diagram for an embodiment of the method of the present invention;

[0080] Figure 4 The following are reactive power curves of some generating units after disturbance in an embodiment of the method of the present invention;

[0081] Figure 5 The BUS-3 converter u after disturbance in the embodiment of the method of the present invention Rq Waveform diagram;

[0082] Figure 6 The above are the active power curves of some generating units after disturbance in an embodiment of the method of the present invention.

[0083] Figure 7 This is a structural diagram of the system of the present invention. Detailed Implementation

[0084] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0085] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0086] Example 1:

[0087] This invention proposes a method for determining the electromagnetic transient small-disturbance stability of a power system, such as... Figure 1 As shown, it includes:

[0088] Step 1: For the power system to be analyzed, establish the state model and algebraic model of the power sources in the power system;

[0089] Step 2: Determine the power source type of each bus in the power system, and construct a coordinate transformation model based on the power source type, state model, and algebraic model of each bus.

[0090] Step 3: Perform π-type equivalent transformation on the power grid transmission lines of the power system and establish branch models;

[0091] Step 4: Based on the coordinate transformation model and branch model, construct the Jacobian matrix of the power system and obtain the eigenvalues ​​of the Jacobian matrix. Based on the eigenvalues, determine the electromagnetic transient small disturbance stability of the power system.

[0092] The power supply types include: synchronous machine type and grid-connected converter type.

[0093] If the power supply type is a synchronous machine, the constructed coordinate transformation model includes: synchronous machine current coordinate transformation model and synchronous machine voltage coordinate transformation model.

[0094] The formula for the synchronous machine current coordinate transformation model is as follows:

[0095]

[0096]

[0097] in, The output current of the d-axis of the synchronous motor connected to bus i is... The output current of the q-axis of the synchronous motor connected to bus i is... δ represents the x-axis component of the output current of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. The x-axis component of the output current of the synchronous machine connected to bus i.

[0098] The formula for the voltage coordinate transformation model of the synchronous machine is as follows:

[0099]

[0100]

[0101] in, Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. δ is the voltage at the d-axis terminal of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. This is the voltage at the q-axis of the synchronous machine connected to bus i.

[0102] If the power supply type is a grid-connected converter, the constructed coordinate transformation model includes: a grid-connected converter current coordinate transformation model and a grid-connected converter voltage coordinate transformation model.

[0103] The formula for the current coordinate transformation model of the grid converter is as follows:

[0104]

[0105]

[0106] in, This refers to the d-axis output current connected to bus i and the grid converter. Let θ be the x-axis component of the output current connected to bus i and the grid converter. i0 The initial phase angle of the grid converter connected to bus i is given. The y-axis component of the output current connected to bus i and the grid converter. This refers to the q-axis output current connected to bus i and the grid converter.

[0107] The formula for the voltage coordinate transformation model of the grid converter is as follows:

[0108]

[0109]

[0110] in, For the voltage component on the x-axis at the point of connection between bus i and the grid-connected converter, Let θ be the d-axis voltage value connected to the grid connection point of the grid-connected converter at bus i. i0 The initial phase angle of the grid converter connected to bus i is given. This represents the q-axis voltage value at the connection point between bus i and the grid-connected converter. The x-axis component represents the voltage at the grid connection point of the grid-connected converter connected to bus i.

[0111] The branch model includes: a series branch model connecting two busbars and a parallel branch model connecting the busbar to the ground.

[0112] The formula for the series branch model is as follows:

[0113]

[0114] in, Let d be the d-axis component of the first derivative of the current flowing from bus A to bus B with respect to time. Z represents the q-axis component of the first time derivative of the current flowing from bus A to bus B. B The impedance reference value is given under rated voltage and rated power, where L is the inductance of the line, and u is the impedance reference value. Ad Let u be the d-axis component of the voltage at bus A. Aq Let u be the q-axis component of the voltage at bus A. Bd Let u be the d-axis component of the voltage at bus B. Bq Let ω be the q-axis component of the voltage at bus B, R be the resistance of the line, and ω be the q-axis component of the voltage at bus B. B This is the reference value for the system's angular frequency.

[0115] The formula for the parallel branch model is as follows:

[0116]

[0117] in, Let be the d-axis component of the first derivative of the bus voltage with respect to time. Let i be the q-axis component of the first derivative of the bus voltage with respect to time. fd i is the d-axis component of the current flowing into the equivalent ground capacitance. fq For the q-axis component of the current flowing into the equivalent capacitance to ground, C f Z is the capacitance value of the equivalent capacitance to ground. B The impedance reference value under rated voltage and rated power, ω B u is the reference value for the system's angular frequency. q U is the q-axis component of the bus voltage. d Let be the d-axis component.

[0118] The present invention will be further described below with reference to embodiments:

[0119] Implementation principle as follows Figure 2 As shown, it includes:

[0120] Step 1: Obtain the circuit topology, power bus number, and power supply type of the system to be analyzed;

[0121] Step 2: Construct the state equations and algebraic equations of the power supply according to different power supply types, specifically as follows:

[0122] Step 2.1: If the power supply is a synchronous machine power supply, the state equations can be written as follows:

[0123]

[0124] With algebraic equations:

[0125]

[0126] Step 2.2: If the power supply is a grid-connected converter, the state equations can be written as follows:

[0127]

[0128]

[0129]

[0130]

[0131] With algebraic equations:

[0132]

[0133] Step 2.3: If the power source is a grid-type converter of virtual synchronization type, the state equations can be written as follows:

[0134]

[0135]

[0136] With algebraic equations:

[0137]

[0138] In the above formulas, the subscript i represents the bus bar number.

[0139] Step 3: Determine the power supply type of each bus in the system. If it is a synchronous machine, the following synchronous machine current coordinate transformation equation needs to be constructed:

[0140]

[0141] Step 4: Determine the power supply type of each bus in the system. If it is a synchronous machine, then the following synchronous machine voltage coordinate transformation equation needs to be constructed:

[0142]

[0143] Step 5: Determine the power supply type of each bus in the system. If it is a grid-connected converter, then the following current coordinate transformation equation for the grid-connected converter needs to be constructed:

[0144]

[0145] Step 6: Determine the power supply type of each bus in the system. If it is a grid-connected converter, then the following voltage coordinate transformation equation for the grid-connected converter needs to be constructed:

[0146]

[0147] Step 7: Determine whether all power sources in the system have been traversed. If there are still power sources for which equations have not been constructed, repeat Step 2 to Step 6.

[0148] Step 8: For system power grid modeling, the transmission lines of the power grid can be represented by a π-type equivalent. For a series branch connecting two buses, it can be written as:

[0149]

[0150] Step 9: For system power grid modeling, for parallel branches from the busbar to ground, it can be written as follows:

[0151]

[0152] Step 10: Organize the state equations and algebraic equations formed in Steps 2 to 9, sort out the state variables, construct the Jacobian matrix of the whole system, and obtain the eigenvalues ​​of the Jacobian matrix.

[0153] The following is an example Figure 3 The following is a further explanation using a typical system as an example:

[0154] The synchronous machine is connected to the BUS-1 bus, the two grid-connected converters are connected to BUS-2 and BUS-3 respectively, and the grid-connected converter is connected to BUS-4.

[0155] By setting a load change at BUS-7, fluctuations in the system's bus voltage, branch current, and power supply can be observed. The time-domain simulation curves are shown below. Figures 4 to 6 As shown. For Figure 4 The reactive power oscillation shown has an oscillation frequency of approximately 52.94 Hz and a damping ratio of approximately 0.1125. For Figure 5 Its oscillation frequency can be measured to be approximately 24.176 Hz, and its damping ratio to be approximately 0.1016. Regarding... Figure 6 The low-frequency oscillation shown has a frequency of approximately 1.1 Hz and a damping ratio of approximately 0.0943.

[0156] The frequency domain analysis results of its typical system are shown in Table 1:

[0157] Table 1

[0158]

[0159] Combining the data in Table 1, it can be seen that the oscillation modes observed in the time-domain simulation at 52.94Hz, 24.176Hz, and 1.1Hz can all be calculated in the frequency-domain analysis, namely: oscillation mode 14# with a damping ratio of 0.11577 and an oscillation frequency of 52.696Hz; oscillation mode 16# with a damping ratio of 0.094517 and an oscillation frequency of 21.501Hz; and oscillation mode 19# with a damping ratio of 0.086959 and an oscillation frequency of 1.2134Hz. From the correlation variables sorted by participation level from high to low, it can be found that oscillation mode 14# is mainly strongly correlated with the reactive power component of the BUS-4 converter, and... Figure 4 The reactive power curves shown are consistent; Oscillation mode 16# is mainly strongly correlated with the active power of the two grid-connected converters BUS-2 and BUS-3. This mode of oscillation can also be observed by observing the q-axis voltage of the grid-connected converter; Oscillation mode 19# is strongly correlated with the synchronous machine excitation voltage, the phase-locked loop of the grid-connected converter, and the active current of the synchronous machine. In terms of frequency band, it is a low-frequency oscillation. From the time domain simulation, it can be seen that it is a relative oscillation between the active power of the synchronous machine and the grid-connected converter. This mode is consistent with the frequency domain and time domain simulations.

[0160] It is evident that frequency domain calculations can effectively obtain information on the various oscillation modes under electromagnetic transients in multi-machine systems, thus aiding in the assessment of system stability.

[0161] Example 2:

[0162] This invention also proposes a system 200 for determining the electromagnetic transient small-disturbance stability of a power system, such as... Figure 7 As shown, it includes:

[0163] The first model building module 201 is used to establish the state model and algebraic model of the power source in the power system to be analyzed.

[0164] The second model building module 202 determines the power supply type of each bus in the power system and constructs a coordinate transformation model based on the power supply type, state model and algebraic model of each bus.

[0165] The third model building module 203 is used to perform π-type equivalent transformation on the power grid transmission lines of the power system and establish a branch model.

[0166] The output module 204 is used to construct the Jacobian matrix of the power system based on the coordinate transformation model and the branch model, obtain the eigenvalues ​​of the Jacobian matrix, and determine the electromagnetic transient small disturbance stability of the power system based on the eigenvalues.

[0167] The power supply types include: synchronous machine type and grid-connected converter type.

[0168] If the power supply type is a synchronous machine, the constructed coordinate transformation model includes: synchronous machine current coordinate transformation model and synchronous machine voltage coordinate transformation model.

[0169] The formula for the synchronous machine current coordinate transformation model is as follows:

[0170]

[0171]

[0172] in, The output current of the d-axis of the synchronous motor connected to bus i is... The output current of the q-axis of the synchronous motor connected to bus i is... δ represents the x-axis component of the output current of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. The x-axis component of the output current of the synchronous machine connected to bus i.

[0173] The formula for the voltage coordinate transformation model of the synchronous machine is as follows:

[0174]

[0175]

[0176] in, Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. δ is the voltage at the d-axis terminal of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. This is the voltage at the q-axis of the synchronous machine connected to bus i.

[0177] If the power supply type is a grid-connected converter, the constructed coordinate transformation model includes: a grid-connected converter current coordinate transformation model and a grid-connected converter voltage coordinate transformation model.

[0178] The formula for the current coordinate transformation model of the grid converter is as follows:

[0179]

[0180]

[0181] in, This refers to the d-axis output current connected to bus i and the grid converter. Let θ be the x-axis component of the output current connected to bus i and the grid converter. i0 The initial phase angle of the grid converter connected to bus i is given. The y-axis component of the output current connected to bus i and the grid converter. This refers to the q-axis output current connected to bus i and the grid converter.

[0182] The formula for the voltage coordinate transformation model of the grid converter is as follows:

[0183]

[0184]

[0185] in, For the voltage component on the x-axis at the point of connection between bus i and the grid-connected converter, Let θ be the d-axis voltage value connected to the grid connection point of the grid-connected converter at bus i. i0 The initial phase angle of the grid converter connected to bus i is given. This represents the q-axis voltage value at the connection point between bus i and the grid-connected converter. The x-axis component represents the voltage at the grid connection point of the grid-connected converter connected to bus i.

[0186] The branch model includes: a series branch model connecting two busbars and a parallel branch model connecting the busbar to the ground.

[0187] The formula for the series branch model is as follows:

[0188]

[0189] in, Let d be the d-axis component of the first derivative of the current flowing from bus A to bus B with respect to time. Z represents the q-axis component of the first time derivative of the current flowing from bus A to bus B. B The impedance reference value is given under rated voltage and rated power, where L is the inductance of the line, and u is the impedance reference value. Ad Let u be the d-axis component of the voltage at bus A. Aq Let u be the q-axis component of the voltage at bus A. Bd Let u be the d-axis component of the voltage at bus B. Bq Let ω be the q-axis component of the voltage at bus B, R be the resistance of the line, and ω be the q-axis component of the voltage at bus B. B This is the reference value for the system's angular frequency.

[0190] The formula for the parallel branch model is as follows:

[0191]

[0192] in, Let be the d-axis component of the first derivative of the bus voltage with respect to time. Let i be the q-axis component of the first derivative of the bus voltage with respect to time. fd i is the d-axis component of the current flowing into the equivalent ground capacitance. fq For the q-axis component of the current flowing into the equivalent capacitance to ground, C f Z is the capacitance value of the equivalent capacitance to ground. B The impedance reference value under rated voltage and rated power, ω B u is the reference value for the system's angular frequency. q U is the q-axis component of the bus voltage. d Let be the d-axis component.

[0193] This invention enables frequency domain analysis and calculation of various broadband oscillation modes by establishing the Jacobian matrix of the electromagnetic transients of the entire system and obtaining the eigenvalues.

[0194] Example 3:

[0195] Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to implement corresponding method flows or corresponding functions, thereby implementing the steps of the methods in the above embodiments.

[0196] Example 4:

[0197] Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiments.

[0198] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0199] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0200] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0201] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0202] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0203] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for determining the electromagnetic transient small-disturbance stability of a power system, characterized in that, The method includes: For the power system to be analyzed, a state model and an algebraic model of the power sources in the power system are established; Determine the power source type of each bus in the power system, and construct a coordinate transformation model based on the power source type, state model, and algebraic model of each bus. The power grid transmission lines of the power system are subjected to π-type equivalent modeling to establish a branch model; Based on the coordinate transformation model and branch model, the Jacobian matrix of the power system is constructed, and the eigenvalues ​​of the Jacobian matrix are obtained. Based on the eigenvalues, the electromagnetic transient small disturbance stability of the power system is determined. The branch model includes: a series branch model connecting two busbars and a parallel branch model connecting a busbar to ground; The formula for the series branch model is as follows: in, Let d be the d-axis component of the first derivative of the current flowing from bus A to bus B with respect to time. Z represents the q-axis component of the first time derivative of the current flowing from bus A to bus B. B The impedance reference value is given under rated voltage and rated power, where L is the inductance of the line, and u is the impedance reference value. Ad Let u be the d-axis component of the voltage at bus A. Aq Let u be the q-axis component of the voltage at bus A. Bd Let u be the d-axis component of the voltage at bus B. Bq Let ω be the q-axis component of the voltage at bus B, R be the resistance of the line, and ω be the q-axis component of the voltage at bus B. B This is the reference value for the system's angular frequency; The formula for the parallel branch model is as follows: in, Let be the d-axis component of the first derivative of the bus voltage with respect to time. Let i be the q-axis component of the first derivative of the bus voltage with respect to time. fd i is the d-axis component of the current flowing into the equivalent ground capacitance. fq For the q-axis component of the current flowing into the equivalent capacitance to ground, C f Z is the capacitance value of the equivalent capacitance to ground. B The impedance reference value under rated voltage and rated power, ω B u is the reference value for the system's angular frequency. q U is the q-axis component of the bus voltage. d Let be the d-axis component.

2. The method according to claim 1, characterized in that, The power supply types include: synchronous machine type and grid-connected converter type.

3. The method according to claim 1, characterized in that, If the power supply type is a synchronous machine, the constructed coordinate transformation model includes: synchronous machine current coordinate transformation model and synchronous machine voltage coordinate transformation model.

4. The method according to claim 3, characterized in that, The formula for the synchronous machine current coordinate transformation model is as follows: in, The output current of the d-axis of the synchronous motor connected to bus i is... The output current of the q-axis of the synchronous motor connected to bus i is... δ represents the x-axis component of the output current of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. The x-axis component of the output current of the synchronous machine connected to bus i.

5. The method according to claim 3, characterized in that, The formula for the voltage coordinate transformation model of the synchronous machine is as follows: in, Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. δ is the voltage at the d-axis terminal of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. This is the voltage at the q-axis of the synchronous machine connected to bus i.

6. The method according to claim 1, characterized in that, If the power supply type is a grid-connected converter, the constructed coordinate transformation model includes: a grid-connected converter current coordinate transformation model and a grid-connected converter voltage coordinate transformation model.

7. The method according to claim 6, characterized in that, The formula for the current coordinate transformation model of the grid-connected converter is as follows: in, This refers to the d-axis output current connected to bus i and the grid converter. Let θ be the x-axis component of the output current connected to bus i and the grid converter. i0 The initial phase angle of the grid converter connected to bus i is given. The y-axis component of the output current connected to bus i and the grid converter. This refers to the q-axis output current connected to bus i and the grid converter.

8. The method according to claim 6, characterized in that, The formula for the voltage coordinate transformation model of the grid-connected converter is as follows: in, For the voltage component on the x-axis at the point of connection between bus i and the grid-connected converter, Let θ be the d-axis voltage value connected to the grid connection point of the grid-connected converter at bus i. i0 The initial phase angle of the grid converter connected to bus i is given. This represents the q-axis voltage value at the connection point between bus i and the grid-connected converter. The x-axis component represents the voltage at the grid connection point of the grid-connected converter connected to bus i.

9. A system for determining the electromagnetic transient small-disturbance stability of a power system, characterized in that, The system includes: The first model building module is used to establish the state model and algebraic model of the power sources in the power system to be analyzed. The second model building module determines the power supply type of each bus in the power system and constructs a coordinate transformation model based on the power supply type, state model and algebraic model of each bus. The third model building module is used to perform π-type equivalent transformation on the power grid transmission lines of the power system and establish branch models. The output module is used to construct the Jacobian matrix of the power system based on the coordinate transformation model and the branch model, obtain the eigenvalues ​​of the Jacobian matrix, and determine the electromagnetic transient small disturbance stability of the power system based on the eigenvalues. The branch model includes: a series branch model connecting two busbars and a parallel branch model connecting a busbar to ground; The formula for the series branch model is as follows: in, Let d be the d-axis component of the first derivative of the current flowing from bus A to bus B with respect to time. Z represents the q-axis component of the first time derivative of the current flowing from bus A to bus B. B The impedance reference value is given under rated voltage and rated power, where L is the inductance of the line, and u is the impedance reference value. Ad Let u be the d-axis component of the voltage at bus A. Aq Let u be the q-axis component of the voltage at bus A. Bd Let u be the d-axis component of the voltage at bus B. Bq Let ω be the q-axis component of the voltage at bus B, R be the resistance of the line, and ω be the q-axis component of the voltage at bus B. B This is the reference value for the system's angular frequency; The formula for the parallel branch model is as follows: in, Let be the d-axis component of the first derivative of the bus voltage with respect to time. Let i be the q-axis component of the first derivative of the bus voltage with respect to time. fd i is the d-axis component of the current flowing into the equivalent ground capacitance. fq For the q-axis component of the current flowing into the equivalent capacitance to ground, C f Z is the capacitance value of the equivalent capacitance to ground. B The impedance reference value under rated voltage and rated power, ω B u is the reference value for the system's angular frequency. q U is the q-axis component of the bus voltage. d Let be the d-axis component.

10. The system according to claim 9, characterized in that, The power supply types include: synchronous machine type and grid-connected converter type.

11. The system according to claim 9, characterized in that, If the power supply type is a synchronous machine, the constructed coordinate transformation model includes: synchronous machine current coordinate transformation model and synchronous machine voltage coordinate transformation model.

12. The system according to claim 11, characterized in that, The formula for the synchronous machine current coordinate transformation model is as follows: in, The output current of the d-axis of the synchronous motor connected to bus i is... The output current of the q-axis of the synchronous motor connected to bus i is... δ represents the x-axis component of the output current of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. The x-axis component of the output current of the synchronous machine connected to bus i.

13. The system according to claim 11, characterized in that, The formula for the voltage coordinate transformation model of the synchronous machine is as follows: in, Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. Let x be the x-axis component of the terminal voltage of the synchronous machine connected to bus i. δ is the voltage at the d-axis terminal of the synchronous machine connected to bus i. i0 The initial value of the power angle of the synchronous machine connected to bus i. This is the voltage at the q-axis of the synchronous machine connected to bus i.

14. The system according to claim 9, characterized in that, If the power supply type is a grid-connected converter, the constructed coordinate transformation model includes: a grid-connected converter current coordinate transformation model and a grid-connected converter voltage coordinate transformation model.

15. The system according to claim 14, characterized in that, The formula for the current coordinate transformation model of the grid-connected converter is as follows: in, This refers to the d-axis output current connected to bus i and the grid converter. Let θ be the x-axis component of the output current connected to bus i and the grid converter. i0 The initial phase angle of the grid converter connected to bus i is given. The y-axis component of the output current connected to bus i and the grid converter. This refers to the q-axis output current connected to bus i and the grid converter.

16. The system according to claim 14, characterized in that, The formula for the voltage coordinate transformation model of the grid-connected converter is as follows: in, For the voltage component on the x-axis at the point of connection between bus i and the grid-connected converter, Let θ be the d-axis voltage value connected to the grid connection point of the grid-connected converter at bus i. i0 The initial phase angle of the grid converter connected to bus i is given. This represents the q-axis voltage value at the connection point between bus i and the grid-connected converter. The x-axis component represents the voltage at the grid connection point of the grid-connected converter connected to bus i.

17. A computer device, characterized in that, include: One or more processors; A processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the method described in any one of claims 1-8 is implemented.

18. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the method as described in any one of claims 1-8.

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