A new energy unit phase-locked loop synchronization stability evaluation method and system of a multi-machine system

Abstract

The application discloses a new energy unit phase-locked loop synchronous stability evaluation method and system of a multi-machine system, which constructs a new energy phase-locked loop output phase angle dynamic equation mathematical model and a synchronous unit steady-state power angle, calculates the new energy end phase-locked loop output phase angle of the multi-machine system before a fault, the synchronous machine power angle when the fault is removed, the new energy unit phase-locked loop output phase angle and the new energy unit phase-locked loop stability limit phase angle, and finally calculates the increasing area and the decreasing area of the new energy phase-locked loop output phase angle of the multi-machine system when the fault is removed, and further determines the new energy unit phase-locked loop synchronous stability, that is, the application combines the synchronous unit to evaluate the phase-locked synchronous stability of the new energy unit in the multi-machine system, improves the evaluation accuracy of the new energy unit phase-locked synchronous stability, and solves the problem that the prior art lacks consideration of the influence of the thermal power unit on the new energy unit in the multi-machine system, thereby resulting in low accuracy of the phase-locked synchronous stability of the new energy power generation unit.

Description

Technical Field

[0001] This invention relates to the field of phase-locked loop (PLL) synchronization and stability assessment for new energy generating units, and particularly to a method and system for assessing the synchronization and stability of PLLs in multi-unit new energy generating units. Background Technology

[0002] With the development of large-scale megawatt-level photovoltaic power generation bases in central and eastern China and the large-scale development of offshore wind power along the coast, joint transmission systems sharing transmission channels between new energy and thermal power are being formed in many regions of my country based on existing power grids. Currently, most new energy power generation units adopt a grid-following control strategy, using a phase-locked loop (PLL) to track the voltage phase angle at the grid connection point to achieve grid connection. When a system fault occurs, the voltage phase angle at the new energy end changes rapidly, which may cause the PLL to fail to track the voltage phase angle, resulting in PLL synchronization instability problems for the new energy units.

[0003] To address the issue of phase-locked loop (PLL) synchronization stability in new energy power generation units, most existing research techniques are applied to single-unit grid-connected new energy systems. These techniques simulate voltage drops at the new energy power plant level caused by faults and analyze the changing trends of the PLL output phase angle motion equation based on the acceleration area and maximum deceleration area during the fault process. This analysis is then used to evaluate the PLL synchronization stability of the new energy power generation unit.

[0004] However, in renewable energy combined with thermal power transmission systems, the voltage at the renewable energy terminal is affected by the nearby thermal power units, thus altering its phase-locked synchronization stability. Current technologies lack consideration for the impact of thermal power units on renewable energy units, resulting in inaccurate phase-locked synchronization stability measurements for renewable energy power generation units. Summary of the Invention

[0005] This invention provides a method and system for evaluating the phase-locked loop synchronization stability of new energy power units in a multi-unit system. It can solve the problem that the existing technology lacks consideration of the impact of thermal power units on new energy power units in a multi-unit system, resulting in low accuracy of the phase-locked loop synchronization stability of new energy power generation units.

[0006] To address the aforementioned technical problems, one embodiment of the present invention provides a method for evaluating the synchronization stability of a phase-locked loop (PLL) in a multi-unit new energy power generation system, comprising:

[0007] Based on the system parameters of the multi-machine system, a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop is constructed.

[0008] Based on the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system failure, calculate the first output phase angle of the phase-locked loop at the new energy terminal before the multi-machine system failure.

[0009] Calculate the second synchronous machine power angle when the multi-machine system fault is cleared based on the first synchronous machine power angle;

[0010] Based on the dynamic equation mathematical model and the second synchronous machine power angle, calculate the second output phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared and the stability limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared;

[0011] Based on the dynamic equation mathematical model, the second synchronous machine power angle, the first output phase angle, and the second output phase angle, the area of ​​the first region is calculated; wherein, the area of ​​the first region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the new energy terminal phase-locked loop from the first output phase angle to the second output phase angle, and the curve corresponding to the d-axis component of the new energy terminal output current;

[0012] Based on the dynamic equation mathematical model, the second synchronous machine power angle, the second output phase angle, and the stable limit phase angle, the area of ​​the second region is calculated; wherein, the area of ​​the second region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the new energy terminal phase-locked loop from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the new energy terminal output current;

[0013] The synchronization stability of the phase-locked loop of the new energy unit is determined based on the area of ​​the first region and the area of ​​the second region.

[0014] Furthermore, the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop is as follows:

[0015]

[0016] Where X1, X2, and X3 represent the line impedances of the multi-machine system; P W U represents the active power of new energy sources; s U represents the infinite bus voltage; d E represents the d-axis component of the voltage of the new energy unit; G δ represents the internal potential of the synchronous generator unit. G Indicates the power angle of the synchronous generator unit; δ W Indicates the output phase angle of the new energy phase-locked loop; i e Indicates the node injection current of the new energy unit; i d This represents the d-axis component of the output current of the new energy generator unit.

[0017] Furthermore, the step of calculating the first output phase angle of the new energy terminal phase-locked loop before the multi-machine system failure, based on the dynamic equation mathematical model and the first synchronizing machine power angle before the multi-machine system failure, includes:

[0018] Let i e equals i dThe power angle of the first synchronous generator unit before the multi-machine system failure is substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and the first output phase angle of the new energy phase-locked loop before the multi-machine system failure is calculated.

[0019] Furthermore, the step of calculating the second synchronizer power angle when the multi-machine system fault is cleared based on the first synchronizer power angle includes:

[0020] Based on the first synchronizing machine power angle, the second synchronizing machine power angle is calculated using the second synchronizing machine power angle calculation formula when the multi-machine system fault is cleared.

[0021] The formula for calculating the power angle of the second synchronizing machine is as follows: δ GC The second synchronizing motor power angle represents the angle of the multi-machine system when a fault is cleared; δ G0 The first synchronous machine power angle is represented by ω; t represents the fault duration; Δt represents the preset step size; ω N T represents the angular velocity of the synchronous machine's rotating shaft. JG P represents the inertial time constant of the synchronous machine. T This indicates the mechanical power of the synchronizing machine.

[0022] Furthermore, the calculation of the second output phase angle of the phase-locked loop of the new energy unit and the stability limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared, based on the dynamic equation mathematical model and the second synchronous machine power angle, includes:

[0023] Let i e equals i d The second synchronous generator unit's power angle before the multi-machine system failure is substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and the second output phase angle of the new energy phase-locked loop when the multi-machine system failure is cleared is calculated.

[0024] Let i e It equals the maximum value of the d-axis component of the output current of the new energy unit, and substitutes the power angle of the second synchronous unit before the multi-machine system fault into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculates the stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared.

[0025] Furthermore, the calculation of the area of ​​the first region satisfies the following formula:

[0026]

[0027] Where, δ W0 Indicates the first output phase angle; δ W1 Indicates the second output phase angle; This represents the d-axis component of the output current of the new energy unit under the second synchronous machine power angle. This indicates the node injection current of the new energy unit under the second synchronous machine power angle; S ac This represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change from the first output phase angle to the second output phase angle at the new energy terminal, and the curve corresponding to the d-axis component of the output current at the new energy terminal.

[0028] Furthermore, the calculation of the area of ​​the second region satisfies the following formula:

[0029]

[0030] Where, δ W1 Indicates the second output phase angle; δ Wcr Indicates the stable limiting phase angle; This represents the d-axis component of the output current of the new energy unit under the second synchronous machine power angle. This indicates the node injection current of the new energy unit under the second synchronous machine power angle; S dc The area enclosed by the phase-locked loop output phase angle characteristic curve when the phase-locked loop at the new energy terminal changes from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the output current at the new energy terminal.

[0031] Furthermore, determining the synchronization stability of the phase-locked loop of the new energy unit based on the area of ​​the first region and the area of ​​the second region includes:

[0032] When the area of ​​the first region is larger than the area of ​​the second region, the phase-locked loop of the new energy unit becomes unstable.

[0033] When the area of ​​the first region is less than or equal to the area of ​​the second region, the new energy unit achieves phase-locked loop synchronization stability.

[0034] Based on the above method embodiments, the present invention provides corresponding system embodiments;

[0035] An embodiment of the present invention provides a phase-locked loop synchronous stability evaluation system for a multi-machine system of new energy generating units, comprising: a dynamic equation mathematical model establishment module, a first calculation module, a second calculation module, a third calculation module, a first region area calculation module, a second region area calculation module, and a stability evaluation module;

[0036] The dynamic equation mathematical model building module is used to construct a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop based on the system parameters of the multi-machine system.

[0037] The first calculation module is used to calculate the first output phase angle of the phase-locked loop at the new energy terminal before the multi-machine system failure, based on the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system failure.

[0038] The second calculation module is used to calculate the second synchronous machine power angle when the multi-machine system fault is cleared, based on the first synchronous machine power angle.

[0039] The third calculation module is used to calculate the second output phase angle of the phase-locked loop of the new energy unit and the stability limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared, based on the dynamic equation mathematical model and the second synchronous machine power angle.

[0040] The first region area calculation module is used to calculate the area of ​​the first region based on the dynamic equation mathematical model, the power angle of the second synchronous machine, the first output phase angle and the second output phase angle; wherein, the area of ​​the first region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop from the first output phase angle to the second output phase angle, and the curve corresponding to the d-axis component of the output current of the new energy terminal;

[0041] The second region area calculation module is used to calculate the area of ​​the second region based on the dynamic equation mathematical model, the power angle of the second synchronous machine, the second output phase angle, and the stable limit phase angle; wherein, the area of ​​the second region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the output current of the new energy terminal;

[0042] The stability assessment module is used to determine the synchronization stability of the phase-locked loop of the new energy unit based on the area of ​​the first region and the area of ​​the second region.

[0043] Furthermore, the third calculation module includes: a second output phase angle calculation unit and a stable limit phase angle calculation unit;

[0044] The second output phase angle calculation unit is used to let i e equals i d The second synchronous generator unit's power angle before the multi-machine system failure was substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and the second output phase angle of the new energy phase-locked loop before the multi-machine system failure was calculated.

[0045] The stability limit phase angle calculation unit is used to let i eIt equals the maximum value of the d-axis component of the output current of the new energy unit, and substitutes the power angle of the second synchronous unit before the multi-machine system fault into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculates the stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared.

[0046] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0047] This invention constructs a mathematical model of the dynamic equation of the phase-locked loop (PLL) output phase angle of the new energy unit, and combines it with the parameters of the synchronous generator unit to calculate the output phase angle of the PLL at the new energy end before a fault in a multi-generator system, the output phase angle of the PLL at the new energy unit when the fault is cleared, and the stability limit phase angle of the PLL at the new energy unit. Finally, based on the output phase angle of the PLL at the new energy end before a fault in the multi-generator system, the output phase angle of the PLL at the new energy unit when the fault is cleared, and the stability limit phase angle of the PLL at the new energy unit, the increase area and decrease area of ​​the output phase angle of the new energy PLL at the fault clearing time are calculated. This determines the synchronization stability of the PLL at the new energy unit in the multi-generator system. In other words, this invention, in conjunction with the synchronous generator unit, evaluates the phase-locked synchronization stability of the new energy units in a multi-generator system, improving the accuracy of the evaluation of the phase-locked synchronization stability of the new energy units. It solves the problem that the existing technology lacks consideration of the impact of thermal power units on new energy units in multi-generator systems, resulting in low accuracy of the phase-locked synchronization stability of new energy power generation units. Attached Figure Description

[0048] Figure 1 : A flowchart illustrating the steps of a phase-locked loop synchronization stability evaluation method for a multi-machine system of new energy generating units, provided by an embodiment of the present invention;

[0049] Figure 2 : A system structure diagram of a phase-locked loop synchronous stability evaluation system for a multi-machine system of new energy generating units provided in an embodiment of the present invention;

[0050] Figure 3 This invention provides an equivalent circuit for a phase-locked loop synchronous stability evaluation system for a multi-machine system of new energy generating units.

[0051] Figure 4 : A block diagram of a phase-locked loop control system for a multi-machine new energy unit provided in an embodiment of the present invention;

[0052] Figure 5 : This is the output phase angle characteristic curve of the new energy phase-locked loop provided in the embodiment of the present invention. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] In the description of this invention, it should be understood that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0055] Example 1:

[0056] Reference Figure 1 The above is a flowchart illustrating the steps of a phase-locked loop synchronization stability evaluation method for a multi-machine system of new energy generating units, provided by an embodiment of the present invention. The method includes at least the following steps:

[0057] Step S1: Based on the system parameters of the multi-machine system, construct a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop;

[0058] In this embodiment, refer to Figure 4 This is a block diagram of a phase-locked loop (PLL) control system for a multi-machine new energy unit provided in an embodiment of the present invention. The dynamic equation for the output phase angle of the new energy PLL is sθ. W =U q (K pPLL +K iPLL / s)+ω0, where s represents the differential operator in the complex frequency domain (s-domain), θ W U represents the phase angle of the new energy phase-locked loop output relative to the stationary shaft, ω0 represents the angular velocity of the synchronous machine's rotating shaft (ω0=1.0), and U q K represents the q-axis component of the terminal voltage of the new energy unit. pPLL K represents the proportional gain of the phase-locked loop. iPLL This represents the integral gain of the phase-locked loop;

[0059] In this embodiment, the dynamic equation of the output phase angle of the new energy phase-locked loop is transformed from the s-domain to the time domain to obtain the dynamic equation of the output phase angle of the new energy phase-locked loop in the time domain, which is as follows: Where, δ S This represents the phase angle between the synchronously rotating axis and the stationary axis;

[0060] In this embodiment, refer to Figure 3 This is an equivalent circuit for a phase-locked loop synchronization stability evaluation system for a multi-machine system of new energy generating units, provided in an embodiment of the present invention. Figure 3 Medium-density thermal power units are synchronous machines, according to Figure 3 It can be known that the output voltage of the new energy power station This is the combined effect of the infinite power source, the synchronous machine, and the new energy power station injecting current into the S, G, and W nodes respectively, denoted as […]. and and and The calculation formula is: Based on the principle of linear network superposition, the voltage at the node end of the new energy power station... for and The sum, i.e., the voltage at the node of the new energy power station. The calculation formula is: Where X1, X2, and X3 represent the line impedances of the multi-machine system; This indicates the internal electromotive force of the synchronous machine; Indicates infinite bus voltage; Indicates the output current of the new energy source;

[0061] In this embodiment, since the renewable energy unit adopts grid voltage orientation, the output current at the renewable energy terminal is decomposed into dq components, and the d-axis component I of the renewable energy terminal output current is obtained. d for q-axis component I q for Taking the d-axis of the new energy terminal voltage as the real axis reference direction, the d-axis component U of the new energy terminal voltage d For U W The q-axis component U of the new energy terminal voltage q Setting it to 0 indicates the voltage at the node end of the new energy power station. In the calculation formula, the voltage at the node end of the new energy power station is decomposed into dq and substituted into I. d I q U d and U q The expressions for the d-axis and q-axis components of the voltage at the node of the new energy power station can be obtained as follows: in, The power factor angle, δ G For the synchronous machine power angle, δ W Output phase angle for new energy phase-locked loop;

[0062] In this embodiment, based on the expressions for the d-axis and q-axis components of the voltage at the node of the new energy power station, U is... q Substituting the dynamic equations for the output phase angle of the new energy phase-locked loop into the time domain, we obtain the following equation:

[0063] Simplifying the formula, we get: Among them, T JPLL D is a custom-named parameter with no specific physical meaning;

[0064] In this embodiment, based on the above equations and expressions, the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop can be obtained, and the specific mathematical expression is as follows:

[0065] Where X1, X2, and X3 represent the line impedances of the multi-machine system; P W U represents the active power of new energy sources; s U represents the infinite bus voltage; d E represents the d-axis component of the voltage of the new energy unit; G δ represents the internal potential of the synchronous generator unit. G Indicates the power angle of the synchronous generator unit; δ W Indicates the output phase angle of the new energy phase-locked loop; i e Indicates the node injection current of the new energy unit; i d K represents the d-axis component of the output current of the new energy unit. pPLL K represents the proportional gain of the phase-locked loop. iPLL d represents the phase-locked loop integral gain; d represents the time-domain differential operator.

[0066] Step S2: Based on the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system failure, calculate the first output phase angle of the phase-locked loop at the new energy terminal before the multi-machine system failure;

[0067] In this embodiment, the line impedance of the multi-machine system, the active power of the new energy source, the infinite bus voltage, the internal potential of the synchronous generator, and the steady-state power angle of the synchronous generator before the fault of the multi-machine system are obtained by measuring the element.

[0068] Let i e equal to l d The system also includes the line impedance of the multi-machine system, the active power of the new energy source, the infinite bus voltage, the internal potential of the synchronous generator, and the steady-state power angle (δ) of the synchronous generator before the multi-machine system fault. G0 Substituting the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop into the mathematical model, the first output phase angle (δ) of the new energy phase-locked loop before the multi-machine system failure is calculated. W0 ); where the steady-state power angle of the synchronizing machine before the multi-machine system failure is the first synchronizing machine power angle before the multi-machine system failure.

[0069] Step S3: Calculate the second synchronous machine power angle when the multi-machine system fault is cleared based on the first synchronous machine power angle;

[0070] In this embodiment, based on the power angle (δ) of the first synchronizing machine G0 The second synchronous machine power angle (δ) during fault clearing in a multi-machine system is calculated using the second synchronous machine power angle calculation formula. GC); where the second synchronizing machine power angle when the multi-machine system fault is cleared represents the synchronizing machine power angle when the multi-machine system fault is cleared; the first synchronizing machine power angle is the measured steady-state synchronizing machine power angle before the multi-machine system fault;

[0071] In this embodiment, the formula for calculating the power angle of the second synchronizing machine is as follows: δ GC The second synchronizing motor power angle represents the angle of the multi-machine system when a fault is cleared; δ G0 The first synchronous machine power angle is represented by ω; t represents the fault duration; Δt represents the preset step size; ω N T represents the angular velocity of the synchronous machine's rotating shaft. JG P represents the inertial time constant of the synchronous machine. T This indicates the mechanical power of the synchronizing machine.

[0072] Step S4: Based on the dynamic equation mathematical model and the second synchronous machine power angle, calculate the second output phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared and the stability limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared;

[0073] In this embodiment, the dynamic equation mathematical model is the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop when a multi-machine system fault is cleared. The specific mathematical expression is as follows:

[0074] Where X1, X2, and X3 represent the line impedances of the multi-machine system; P W U represents the active power of new energy sources; s U represents the infinite bus voltage; d E represents the d-axis component of the voltage of the new energy unit; G δ represents the internal potential of the synchronous generator unit. GC This represents the power angle of the second synchronizing machine, i.e., the power angle of the synchronizing machine when a fault in the multi-machine system is cleared; δ W Indicates the output phase angle of the new energy phase-locked loop; i e Indicates the node injection current of the new energy unit; i d The d-axis component represents the output current of the new energy generator unit;

[0075] In this embodiment, the line impedance of the multi-machine system, the active power of the new energy source, the infinite bus voltage, and the internal potential of the synchronous generator are obtained through measuring elements, and i e equals i dThe line impedance of the multi-machine system, the active power of the new energy source, the infinite bus voltage, the electromotive force of the synchronous generator unit, and the power angle of the second synchronous generator unit before the multi-machine system fault are substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop when the multi-machine system fault is cleared. The second output phase angle (δ) of the new energy terminal phase-locked loop when the multi-machine system fault is cleared is calculated. W1 ); where the second output phase angle is the output phase angle of the phase-locked loop at the new energy end when the multi-machine system fault is cleared;

[0076] In this embodiment, the line impedance of the multi-machine system, the active power of the new energy source, the infinite bus voltage, and the internal potential of the synchronous generator are obtained through measuring elements, and i e The maximum value of the d-axis component of the output current of the new energy unit is equal to that of the new energy unit. The line impedance of the multi-unit system, the active power of the new energy unit, the infinite bus voltage, the internal potential of the synchronous generator unit, and the power angle of the second synchronous generator unit before the multi-unit system fault are substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy unit's phase-locked loop when the multi-unit system fault is cleared. The stability limit phase angle (δ) of the new energy unit's phase-locked loop when the multi-unit system fault is cleared is then calculated. Wcr ).

[0077] Step S5: Calculate the area of ​​the first region based on the dynamic equation mathematical model, the power angle of the second synchronous machine, the first output phase angle, and the second output phase angle; wherein, the area of ​​the first region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop from the first output phase angle to the second output phase angle, and the curve corresponding to the d-axis component of the output current of the new energy terminal.

[0078] In this embodiment, the calculation of the area S of the first region... ac The following calculation formula must be satisfied:

[0079]

[0080] Where, δ W0 Indicates the first output phase angle; δ W1 Indicates the second output phase angle; This represents the d-axis component of the output current of the new energy unit under the second synchronous machine power angle. This indicates the node injection current of the new energy unit under the second synchronous machine power angle; refer to Figure 5 : This is the output phase angle characteristic curve of the new energy phase-locked loop provided in the embodiment of the present invention, S ac This represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change from the first output phase angle to the second output phase angle at the new energy terminal, and the curve corresponding to the d-axis component of the output current at the new energy terminal.

[0081] Step S6: Calculate the area of ​​the second region based on the dynamic equation mathematical model, the power angle of the second synchronous machine, the second output phase angle, and the stable limit phase angle; wherein, the area of ​​the second region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the output current of the new energy terminal;

[0082] In this embodiment, the calculation of the area S of the second region... dc The following calculation formula must be satisfied:

[0083]

[0084] Where, δ W1 Indicates the second output phase angle; δ Wcr Indicates the stable limiting phase angle; This represents the d-axis component of the output current of the new energy unit under the second synchronous machine power angle. This indicates the node injection current of the new energy unit under the second synchronous machine power angle; refer to Figure 5 : This is the output phase angle characteristic curve of the new energy phase-locked loop provided in the embodiment of the present invention, S dc The area enclosed by the phase-locked loop output phase angle characteristic curve when the phase-locked loop at the new energy terminal changes from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the output current at the new energy terminal.

[0085] Step S7: Determine the synchronization stability of the phase-locked loop of the new energy unit based on the area of ​​the first region and the area of ​​the second region;

[0086] In this embodiment, when the area of ​​the first region is greater than the area of ​​the second region, the phase angle output by the phase-locked loop of the new energy unit has no steady-state solution, and the phase-locked loop of the new energy unit becomes synchronously unstable; when the area of ​​the first region is less than or equal to the area of ​​the second region, the phase angle output by the phase-locked loop of the new energy unit has no steady-state solution, and the phase-locked loop of the new energy unit becomes synchronously stable.

[0087] Example 2:

[0088] Reference Figure 2 The above is a system structure diagram of a phase-locked loop synchronous stability evaluation system for a multi-machine system of new energy generating units, provided by an embodiment of the present invention. The system includes: a dynamic equation mathematical model establishment module, a first calculation module, a second calculation module, a third calculation module, a first region area calculation module, a second region area calculation module, and a stability evaluation module.

[0089] The dynamic equation mathematical model building module is used to construct a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop based on the system parameters of the multi-machine system.

[0090] The first calculation module is used to calculate the first output phase angle of the phase-locked loop at the new energy terminal before the multi-machine system failure, based on the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system failure.

[0091] The second calculation module is used to calculate the second synchronous machine power angle when the multi-machine system fault is cleared, based on the first synchronous machine power angle.

[0092] The third calculation module is used to calculate the second output phase angle of the phase-locked loop of the new energy unit and the stability limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared, based on the dynamic equation mathematical model and the second synchronous machine power angle.

[0093] The first region area calculation module is used to calculate the area of ​​the first region based on the dynamic equation mathematical model, the power angle of the second synchronous machine, the first output phase angle and the second output phase angle; wherein, the area of ​​the first region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop from the first output phase angle to the second output phase angle, and the curve corresponding to the d-axis component of the output current of the new energy terminal;

[0094] The second region area calculation module is used to calculate the area of ​​the second region based on the dynamic equation mathematical model, the power angle of the second synchronous machine, the second output phase angle, and the stable limit phase angle; wherein, the area of ​​the second region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the output current of the new energy terminal;

[0095] The stability assessment module is used to determine the synchronization stability of the phase-locked loop of the new energy unit based on the area of ​​the first region and the area of ​​the second region.

[0096] In this embodiment, the third calculation module includes: a second output phase angle calculation unit and a stable limit phase angle calculation unit;

[0097] The second output phase angle calculation unit is used to let i e equals i d The second synchronous generator unit's power angle before the multi-machine system failure was substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and the second output phase angle of the new energy phase-locked loop before the multi-machine system failure was calculated.

[0098] The stability limit phase angle calculation unit is used to let i eIt equals the maximum value of the d-axis component of the output current of the new energy unit, and substitutes the power angle of the second synchronous unit before the multi-machine system fault into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculates the stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared.

[0099] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for evaluating the synchronization stability of phase-locked loops in a multi-machine system of new energy generating units, characterized in that, include: Based on the system parameters of the multi-machine system, a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop is constructed. Based on the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system failure, calculate the first output phase angle of the phase-locked loop at the new energy terminal before the multi-machine system failure. Calculate the second synchronous machine power angle when the multi-machine system fault is cleared based on the first synchronous machine power angle; Based on the dynamic equation mathematical model and the second synchronous machine power angle, calculate the second output phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared and the stability limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared; Based on the dynamic equation mathematical model, the second synchronous machine power angle, the first output phase angle, and the second output phase angle, the area of ​​the first region is calculated; wherein, the area of ​​the first region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the new energy terminal phase-locked loop from the first output phase angle to the second output phase angle, and the curve corresponding to the d-axis component of the new energy terminal output current; Based on the dynamic equation mathematical model, the second synchronous machine power angle, the second output phase angle, and the stable limit phase angle, the area of ​​the second region is calculated; wherein, the area of ​​the second region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the new energy terminal phase-locked loop from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the new energy terminal output current; The synchronization stability of the phase-locked loop of the new energy unit is determined based on the area of ​​the first region and the area of ​​the second region.

2. The method for evaluating the synchronization stability of a phase-locked loop in a multi-machine system for new energy generating units according to claim 1, characterized in that, The mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop is as follows: Where X1, X2, and X3 represent the line impedance of the multi-machine system; P W U represents the active power of new energy sources; S U represents the infinite bus voltage; d E represents the d-axis component of the voltage of the new energy unit; G δ represents the internal potential of the synchronous generator unit. G Indicates the power angle of the synchronous generator unit; δ W Indicates the output phase angle of the new energy phase-locked loop; i e Indicates the node injection current of the new energy unit; i d This represents the d-axis component of the output current of the new energy generator unit.

3. The method for evaluating the synchronization stability of a phase-locked loop in a multi-machine system for new energy generating units according to claim 2, characterized in that, The step of calculating the first output phase angle of the phase-locked loop at the new energy source before the multi-machine system failure, based on the dynamic equation mathematical model and the first synchronizing machine power angle before the multi-machine system failure, includes: Let i e equals i d The power angle of the first synchronous generator unit before the multi-machine system failure is substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and the first output phase angle of the new energy phase-locked loop before the multi-machine system failure is calculated.

4. The method for evaluating the synchronization stability of a phase-locked loop in a multi-machine system for new energy generating units according to claim 1, characterized in that, The calculation of the second synchronous machine power angle during multi-machine system fault clearing based on the first synchronous machine power angle includes: Based on the first synchronizing machine power angle, the second synchronizing machine power angle is calculated using the second synchronizing machine power angle calculation formula when the multi-machine system fault is cleared. The formula for calculating the power angle of the second synchronizing machine is as follows: δ GC The second synchronizing motor power angle represents the angle of the multi-machine system when a fault is cleared; δ G0 The first synchronous machine power angle is represented by ω; t represents the fault duration; Δt represents the preset step size; ω N T represents the angular velocity of the synchronous machine's rotating shaft. JG P represents the inertial time constant of the synchronous machine. T This indicates the mechanical power of the synchronizing machine.

5. The method for evaluating the synchronization stability of a phase-locked loop in a multi-machine system for new energy generating units according to claim 2, characterized in that, The calculation of the second output phase angle of the phase-locked loop of the new energy unit and the stability limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared, based on the dynamic equation mathematical model and the second synchronous machine power angle, includes: Let i e equals i d The second synchronous generator unit's power angle before the multi-machine system failure was substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and the second output phase angle of the new energy phase-locked loop before the multi-machine system failure was calculated. Let i e It equals the maximum value of the d-axis component of the output current of the new energy unit, and substitutes the power angle of the second synchronous unit before the multi-machine system fault into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculates the stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared.

6. The method for evaluating the synchronization stability of a phase-locked loop in a multi-machine system for new energy generating units according to claim 1, characterized in that, The calculation of the area of ​​the first region satisfies the following formula: Where, δ W0 Indicates the first output phase angle; δ W1 Indicates the second output phase angle; This represents the d-axis component of the output current of the new energy unit under the second synchronous machine power angle. This indicates the node injection current of the new energy unit under the second synchronous machine power angle; S ac This represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change from the first output phase angle to the second output phase angle at the new energy terminal, and the curve corresponding to the d-axis component of the output current at the new energy terminal.

7. The method for evaluating the synchronization stability of a phase-locked loop in a multi-machine system for new energy generating units according to claim 1, characterized in that, The calculation of the area of ​​the second region satisfies the following formula: Where, δ W1 Indicates the second output phase angle; δ Wcr Indicates the stable limiting phase angle; This represents the d-axis component of the output current of the new energy unit under the second synchronous machine power angle. This indicates the node injection current of the new energy unit under the second synchronous machine power angle; S dc The area enclosed by the phase-locked loop output phase angle characteristic curve when the phase-locked loop at the new energy terminal changes from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the output current at the new energy terminal.

8. The method for evaluating the synchronization stability of a phase-locked loop in a multi-machine system for new energy generating units according to claim 1, characterized in that, The determination of the phase-locked loop synchronization stability of the new energy unit based on the area of ​​the first region and the area of ​​the second region includes: When the area of ​​the first region is larger than the area of ​​the second region, the phase-locked loop of the new energy unit becomes unstable. When the area of ​​the first region is less than or equal to the area of ​​the second region, the new energy unit achieves phase-locked loop synchronization stability.

9. A phase-locked loop synchronization stability evaluation system for multi-machine new energy generating units, characterized in that, include: The system includes a dynamic equation mathematical model establishment module, a first calculation module, a second calculation module, a third calculation module, a first region area calculation module, a second region area calculation module, and a stability assessment module. The dynamic equation mathematical model building module is used to construct a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop based on the system parameters of the multi-machine system. The first calculation module is used to calculate the first output phase angle of the phase-locked loop at the new energy terminal before the multi-machine system failure, based on the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system failure. The second calculation module is used to calculate the second synchronous machine power angle when the multi-machine system fault is cleared, based on the first synchronous machine power angle. The third calculation module is used to calculate the second output phase angle of the phase-locked loop of the new energy unit and the stability limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared, based on the dynamic equation mathematical model and the second synchronous machine power angle. The first region area calculation module is used to calculate the area of ​​the first region based on the dynamic equation mathematical model, the power angle of the second synchronous machine, the first output phase angle and the second output phase angle; wherein, the area of ​​the first region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop from the first output phase angle to the second output phase angle, and the curve corresponding to the d-axis component of the output current of the new energy terminal; The second region area calculation module is used to calculate the area of ​​the second region based on the dynamic equation mathematical model, the power angle of the second synchronous machine, the second output phase angle, and the stable limit phase angle; wherein, the area of ​​the second region is: the area enclosed between the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop from the second output phase angle to the stable limit phase angle, and the curve corresponding to the d-axis component of the output current of the new energy terminal; The stability assessment module is used to determine the synchronization stability of the phase-locked loop of the new energy unit based on the area of ​​the first region and the area of ​​the second region.

10. The phase-locked loop synchronization stability evaluation system for a multi-machine system of new energy generating units according to claim 9, characterized in that, The third calculation module includes: a second output phase angle calculation unit and a stable limit phase angle calculation unit; The second output phase angle calculation unit is used for i e equals i d The second synchronous generator unit's power angle before the multi-machine system failure was substituted into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and the second output phase angle of the new energy phase-locked loop before the multi-machine system failure was calculated. The stability limit phase angle calculation unit is used to let i e It equals the maximum value of the d-axis component of the output current of the new energy unit, and substitutes the power angle of the second synchronous unit before the multi-machine system fault into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculates the stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system fault is cleared.

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