Method and system for evaluating synchronous stability of phase-locked loop of new energy unit of multi-machine system

Abstract

The invention discloses a multi-machine system new energy unit phase-locked loop synchronization stability evaluation method and system, and the method comprises the steps: constructing a new energy phase-locked loop output phase angle dynamic equation mathematical model and a synchronization unit steady state power angle; calculating a new energy end phase-locked loop output phase angle before the fault of the multi-machine system, a synchronous machine power angle when the fault is removed, a new energy unit phase-locked loop output phase angle and a new energy unit phase-locked loop stability limit phase angle, and finally calculating an increased area and a reduced area of the new energy phase-locked loop output phase angle when the fault of the multi-machine system is removed. According to the method, the synchronous unit is combined to evaluate the phase-locked synchronous stability of the new energy unit in the multi-machine system, so that the evaluation accuracy of the phase-locked synchronous stability of the new energy unit is improved, and the problem that the influence of a thermal power generating unit on the new energy unit is not considered in the multi-machine system in the prior art is solved; and the accuracy of the phase locking synchronization stability of the new energy power generation unit is not high.

Description

Technical Field

[0001] The present invention relates to the field of phase-locked loop synchronization stability assessment for new energy units, and in particular to a phase-locked loop synchronization stability assessment method and system for new energy units in a multi-machine system. Background Art

[0002] With the development of large-scale million-kilowatt photovoltaic power generation bases in the central and eastern regions and large-scale offshore wind power development in coastal areas, a joint transmission system that uses a shared transmission channel for new energy and thermal power is being formed in many regions of my country based on the existing transmission grid. Among them, most new energy power generation units currently adopt a grid-following control strategy, and achieve grid connection through a phase-locked loop (PLL) tracking the voltage phase angle at the grid connection point. When a system failure occurs, the voltage phase angle of the new energy terminal changes rapidly, and the phase-locked loop may be unable to track the terminal voltage phase angle. At this time, the new energy unit will experience a phase-locked loop synchronization instability problem.

[0003] To address the phase-locked synchronization stability issue of renewable energy power generation units, existing research technologies are mostly applied to the scenario of new energy single-machine grid-connected systems. By simulating the voltage drop phenomenon at the renewable energy station end caused by faults, the change trend of the phase angle motion equation of the new energy phase-locked loop output is analyzed according to the acceleration area and maximum deceleration area of ​​the phase-locked loop during the fault process, thereby evaluating the phase-locked synchronization stability of the renewable energy power generation unit.

[0004] However, in the new energy combined thermal power transmission system, the voltage at the new energy terminal is affected by the adjacent thermal power units, so its phase-locked synchronization stability will also change. However, the existing technology lacks consideration of the impact of thermal power units on new energy units, resulting in low accuracy of the phase-locked synchronization stability of new energy power generation units. Summary of the invention

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

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system, comprising:

[0007] According to 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] Calculate the first output phase angle of the phase-locked loop at the new energy end before the multi-machine system fails according to the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system fails;

[0009] Calculating a second synchronous machine power angle when a multi-machine system fault is cleared according to the first synchronous machine power angle;

[0010] Calculate the second output phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed and the stable limit phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed according to the dynamic equation mathematical model and the second synchronous machine power angle;

[0011] The area of ​​the first region is calculated according to the dynamic equation mathematical model, the second synchronous machine power angle, the first output phase angle and the second output phase angle; wherein the area of ​​the first region is the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 at the new energy end;

[0012] The area of ​​the second region is calculated according to the dynamic equation mathematical model, the second synchronous machine power angle, the second output phase angle and the stable limit phase angle; wherein the area of ​​the second region is the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 end;

[0013] The synchronization stability of the phase-locked loop of the new energy generator set is determined according to 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] Among them, X 1 , X 2 and X 3 Represents the line impedance of the multi-machine system; P W Indicates the active power of new energy; U s Indicates infinite bus voltage; U d Represents the d-axis component of the voltage of the new energy unit; E G Represents the potential inside the synchronous unit; δ G Indicates the power angle of the synchronous unit; δ W Represents the output phase angle of the new energy phase-locked loop; i e Represents the node injection current of the new energy unit; i d Represents the d-axis component of the output current of the new energy unit.

[0017] Further, the first output phase angle of the phase-locked loop at the new energy end before the multi-machine system fails is calculated based on the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system fails, including:

[0018] Let i eEqual to i d The power angle of the first synchronous 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 phase-locked loop at the new energy end before the multi-machine system failure is calculated.

[0019] Further, the calculating of the second synchronous machine power angle when the multi-machine system fault is removed according to the first synchronous machine power angle includes:

[0020] According to the first synchronous machine power angle, a second synchronous machine power angle when a multi-machine system fault is removed is calculated by a second synchronous machine power angle calculation formula;

[0021] The calculation formula of the second synchronous machine power angle is as follows: δ GC Indicates the power angle of the second synchronous machine when the multi-machine system fails; δ G0 represents the first synchronous machine power angle; t represents the fault duration; Δt represents the preset step size; ω N Indicates the angular velocity of the synchronous machine's rotating shaft; T JG Indicates the inertia time constant of the synchronous machine; P T Indicates the mechanical power of the synchronous machine.

[0022] Further, the second output phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed and the stable limit phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed are calculated according to the dynamic equation mathematical model and the second synchronous machine power angle, including:

[0023] Let i e Equal to i d , and substitute the power angle of the second synchronous unit before the multi-machine system failure into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculate the second output phase angle of the phase-locked loop at the new energy end when the multi-machine system failure is removed;

[0024] Let i e It is equal to the maximum value of the d-axis component of the output current of the new energy unit, and the power angle of the second synchronous 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 stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system failure is removed is calculated.

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

[0026]

[0027] Among them, δ W0 represents the first output phase angle; δ W1 represents the second output phase angle; represents the d-axis component of the output current of the new energy generator set at the second synchronous machine power angle; represents the node injection current of the new energy generator set at the second synchronous machine power angle; S ac It represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to when the new energy end phase-locked loop changes 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 end output current.

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

[0029]

[0030] Among them, δ W1 represents the second output phase angle; δ Wcr represents the stable limiting phase angle; represents the d-axis component of the output current of the new energy generator set at the second synchronous machine power angle; represents the node injection current of the new energy generator set at the second synchronous machine power angle; S dc It represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to when the new energy end phase-locked loop changes 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 end output current.

[0031] Further, the determining of the phase-locked loop synchronization stability of the new energy generator set according to 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 that of the second region, the phase-locked loop synchronization instability of the new energy unit occurs;

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

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

[0035] An embodiment of the present invention provides a phase-locked loop synchronous stability assessment system for a new energy generator set of a multi-machine system, 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 assessment module;

[0036] The dynamic equation mathematical model building module is used to build a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop according to 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 end before the multi-machine system fails according to the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system fails;

[0038] The second calculation module is used to calculate the second synchronous machine power angle when the multi-machine system fault is removed according to 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 generator set when the multi-machine system fault is removed and the stable limit phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed according to the dynamic equation mathematical model and the second synchronous machine power angle;

[0040] The first region area calculation module is used to calculate the first region area according to the dynamic equation mathematical model, the second synchronous machine power angle, the first output phase angle and the second output phase angle; wherein the first region area is: the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 at the new energy end;

[0041] The second region area calculation module is used to calculate the second region area according to the dynamic equation mathematical model, the second synchronous machine power angle, the second output phase angle and the stable limit phase angle; wherein the second region area is: the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 end;

[0042] The stability evaluation module is used to determine the synchronization stability of the phase-locked loop of the new energy generator set according to the area of ​​the first region and the area of ​​the second region.

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

[0044] The second output phase angle calculation unit is used to set i e Equal to i d , and substitute the power angle of the second synchronous unit before the multi-machine system failure into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculate the second output phase angle of the phase-locked loop at the new energy end before the multi-machine system failure;

[0045] The stability limit phase angle calculation unit is used to set i eIt is equal to the maximum value of the d-axis component of the output current of the new energy unit, and the power angle of the second synchronous 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 stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system failure is removed is calculated.

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

[0047] The present invention constructs a mathematical model of a dynamic equation of a phase-locked loop output phase angle of a new energy source, and combines the parameters of a synchronous unit to calculate the phase-locked loop output phase angle of a new energy source end of a multi-machine system before a fault, the phase-locked loop output phase angle of a new energy source unit when a fault is removed, and a phase-locked loop stability limit phase angle of the new energy source unit. Finally, the increase area and the decrease area of ​​the phase-locked loop output phase angle of the new energy source when the fault is removed in the multi-machine system are calculated according to the phase-locked loop output phase angle of the new energy source end of the multi-machine system before a fault, the phase-locked loop output phase angle of the new energy source unit when a fault is removed, and the phase-locked loop stability limit phase angle of the new energy source unit, so as to determine the phase-locked loop synchronization stability of the new energy source unit in the multi-machine system. That is, the present invention combines a synchronous unit to evaluate the phase-locked synchronization stability of the new energy source unit in the multi-machine system, improves the evaluation accuracy of the phase-locked synchronization stability of the new energy source unit, and solves the problem that the prior art lacks consideration of the influence of thermal power units on new energy units in a multi-machine system, resulting in low accuracy of the phase-locked synchronization stability of the new energy power generation unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 : A flowchart of a method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system 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 new energy generator set in a multi-machine system provided by an embodiment of the present invention;

[0050] Figure 3 : An equivalent circuit of a phase-locked loop synchronous stability evaluation system for a new energy generator set in a multi-machine system provided by an embodiment of the present invention;

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

[0052] Figure 5 : The output phase angle characteristic curve of the new energy phase-locked loop provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0055] Embodiment 1:

[0056] Reference Figure 1 , is a flowchart of a method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system provided by an embodiment of the present invention, the method comprising at least the following steps:

[0057] Step S1: constructing a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop according to the system parameters of the multi-machine system;

[0058] In this embodiment, refer to Figure 4 , is a phase-locked loop control block diagram of a new energy unit in a multi-machine system provided by an embodiment of the present invention, and the dynamic equation of the output phase angle of the new energy phase-locked loop is sθ W =U q (K pPLL +K iPLL / s)+ω 0 , where s represents the differential operator in the complex frequency domain (s domain), θ W Represents the phase angle of the new energy phase-locked loop relative to the stationary axis output, ω 0 represents the angular velocity of the synchronous machine shaft (ω0=1.0), U q Represents the q-axis component of the voltage at the terminal of the new energy unit, K pPLL Represents the phase-locked loop proportional gain, K iPLL Represents the phase-locked loop integral gain;

[0059] In this embodiment, the output phase angle dynamic equation of the new energy phase-locked loop is converted from the s-domain to the time-domain to obtain the output phase angle dynamic equation of the new energy phase-locked loop in the time-domain, which is as follows: Among them, δ S It indicates the phase angle of the synchronous rotating axis relative to the stationary axis;

[0060] In this embodiment, refer to Figure 3 , is an equivalent circuit of a phase-locked loop synchronous stability evaluation system for a new energy generator set in a multi-machine system provided by an embodiment of the present invention, Figure 3 The medium-sized thermal power unit is a synchronous machine. Figure 3 It can be known that the outlet voltage of the new energy station It is the joint result of the infinite power source, synchronous machine and new energy station injecting current into S, G and W nodes respectively, which are recorded as and and and The calculation formula is: According to the linear network superposition principle, the voltage at the node end of the new energy station for and The sum of the voltage at the node of the new energy station is The calculation formula is: Among them, X 1 , X 2 and X 3 Indicates the line impedance of a multi-machine system; It represents the potential inside the synchronous machine; Represents infinite bus voltage; Indicates the new energy output current;

[0061] In this embodiment, since the new energy generator set adopts grid voltage orientation, the output current of the new energy terminal is decomposed into dq, and the d-axis component I of the output current of the new energy terminal is 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 of the new energy terminal voltage U d For U W , the q-axis component of the new energy terminal voltage U q Set to 0, the voltage at the node of the new energy station The voltage at the node end of the new energy station is decomposed into dq in the calculation formula and substituted into I d ,I q , U d and U q The expressions of the d-axis component and q-axis component of the node voltage of the new energy station can be obtained: in, is the power factor angle, δ G is the synchronous machine power angle, δ W Output phase angle for new energy phase-locked loop;

[0062] In this embodiment, according to the expressions of the d-axis component and the q-axis component of the node terminal voltage of the new energy station, U q Substituting the output phase angle dynamic equation of the new energy phase-locked loop into the time domain, the following equation can be obtained:

[0063]

[0064] Simplifying the formula, we get: Among them, T JPLL and D are user-defined named parameters with no specific physical meaning;

[0065] In this embodiment, according to the above equations and expressions, a mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop can be obtained. The specific mathematical expression is as follows:

[0066] Among them, X 1 , X 2 and X 3 Represents the line impedance of the multi-machine system; P W Indicates the active power of new energy; U s Indicates infinite bus voltage; U d Represents the d-axis component of the voltage of the new energy unit; E G Represents the potential inside the synchronous unit; δ G Indicates the power angle of the synchronous unit; δ W Represents the output phase angle of the new energy phase-locked loop; i e Represents the node injection current of the new energy unit; i d Represents the d-axis component of the output current of the new energy unit; K pPLL Represents the phase-locked loop proportional gain, K iPLL represents the phase-locked loop integral gain; d represents the time domain differential operator.

[0067] Step S2: Calculate the first output phase angle of the phase-locked loop at the new energy end before the multi-machine system fails according to the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system fails;

[0068] In this embodiment, the line impedance of the multi-machine system, the active power of the new energy, the infinite bus voltage, the internal potential of the synchronous unit and the steady-state power angle of the synchronous machine before the multi-machine system fails are obtained by measuring the components;

[0069] Let i e Equal to l d The line impedance of the multi-machine system, the active power of new energy, the infinite bus voltage, the internal potential of the synchronous unit, and the steady-state power angle (δ G0 ) 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 (δ W0 );Wherein, the steady-state power angle of the synchronous machine before the multi-machine system failure is the first synchronous machine power angle before the multi-machine system failure.

[0070] Step S3: Calculating a second synchronous machine power angle when a multi-machine system fault is cleared according to the first synchronous machine power angle;

[0071] In this embodiment, according to the first synchronous machine power angle (δ G0 ), and the second synchronous machine power angle (δ GC ); wherein the second synchronous machine power angle when the multi-machine system fault is removed represents the synchronous machine power angle when the multi-machine system fault is removed; the first synchronous machine power angle is the synchronous machine steady-state power angle obtained by measurement before the multi-machine system fault;

[0072] In this embodiment, the second synchronous machine power angle calculation formula is as follows: δ GC Indicates the power angle of the second synchronous machine when the multi-machine system fails; δ G0 represents the first synchronous machine power angle; t represents the fault duration; Δt represents the preset step size; ω N Indicates the angular velocity of the synchronous machine's rotating shaft; T JG Indicates the inertia time constant of the synchronous machine; P T Indicates the mechanical power of the synchronous machine.

[0073] Step S4: Calculate the second output phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed and the stability limit phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed according to the dynamic equation mathematical model and the second synchronous machine power angle;

[0074] In this embodiment, the dynamic equation mathematical model is a 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 removed. The mathematical expression is specifically as follows:

[0075] Among them, X 1 , X 2 and X 3 Represents the line impedance of the multi-machine system; P W Indicates the active power of new energy; U s Indicates infinite bus voltage; U d Represents the d-axis component of the voltage of the new energy unit; E G Represents the potential inside the synchronous unit; δ GC represents the second synchronous machine power angle, that is, the synchronous machine power angle when the multi-machine system fault is removed; δ W Represents the output phase angle of the new energy phase-locked loop; i e Represents the node injection current of the new energy unit; i d Represents the d-axis component of the output current of the new energy unit;

[0076] In this embodiment, the line impedance, new energy active power, infinite bus voltage and internal potential of the synchronous unit of the multi-machine system are obtained by measuring the components.e Equal to i d The line impedance of the multi-machine system, the active power of the new energy, the infinite bus voltage, the potential inside the synchronous unit and the power angle of the second synchronous 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 removed, and the second output phase angle (δ W1 ); wherein the second output phase angle is the output phase angle of the phase-locked loop at the new energy end when a multi-machine system fault is removed;

[0077] In this embodiment, the line impedance, new energy active power, infinite bus voltage and internal potential of the synchronous unit of the multi-machine system are obtained by measuring the components. e The maximum value of the d-axis component of the output current of the new energy unit is equal to the line impedance of the multi-machine system, the active power of the new energy unit, the infinite bus voltage, the potential inside the synchronous unit and the power angle of the second synchronous 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 removed, and the stable limit phase angle (δ Wcr ).

[0078] Step S5: Calculate the area of ​​the first region according to the dynamic equation mathematical model, the second synchronous machine power angle, the first output phase angle and the second output phase angle; wherein the area of ​​the first region is the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 at the new energy end;

[0079] In this embodiment, the calculation of the first region area S ac Satisfies the following calculation formula:

[0080]

[0081] Among them, δ W0 represents the first output phase angle; δ W1 represents the second output phase angle; represents the d-axis component of the output current of the new energy generator set at the second synchronous machine power angle; Indicates the node injection current of the new energy unit under the second synchronous machine power angle; refer to Figure 5 : is the output phase angle characteristic curve of the new energy phase-locked loop provided in the embodiment of the present invention, S ac It represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to when the new energy end phase-locked loop changes 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 end output current.

[0082] Step S6: Calculate the area of ​​the second region according to the dynamic equation mathematical model, the second synchronous machine power angle, the second output phase angle and the stable limit phase angle; wherein the area of ​​the second region is: the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 end;

[0083] In this embodiment, the second region area S is calculated dc Satisfies the following calculation formula:

[0084]

[0085] Among them, δ W1 represents the second output phase angle; δ Wcr represents the stable limiting phase angle; represents the d-axis component of the output current of the new energy generator set at the second synchronous machine power angle; Indicates the node injection current of the new energy unit under the second synchronous machine power angle; refer to Figure 5 : is the output phase angle characteristic curve of the new energy phase-locked loop provided in the embodiment of the present invention, S dc It represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to when the new energy end phase-locked loop changes 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 end output current.

[0086] Step S7: determining the synchronization stability of the phase-locked loop of the new energy generator set according to the area of ​​the first region and the area of ​​the second region;

[0087] In this embodiment, when the area of ​​the first region is larger than that of the second region, the phase-locked loop output phase angle of the new energy unit has no steady-state solution, and the phase-locked loop synchronization of the new energy unit becomes unstable; when the area of ​​the first region is less than or equal to that of the second region, the phase-locked loop output phase angle of the new energy unit has no steady-state solution, and the phase-locked loop synchronization of the new energy unit becomes stable.

[0088] Embodiment 2:

[0089] Reference Figure 2 , which is a system structure diagram of a phase-locked loop synchronous stability assessment system for a new energy unit of a multi-machine system 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 assessment module;

[0090] The dynamic equation mathematical model building module is used to build a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop according to the system parameters of the multi-machine system;

[0091] The first calculation module is used to calculate the first output phase angle of the phase-locked loop at the new energy end before the multi-machine system fails according to the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system fails;

[0092] The second calculation module is used to calculate the second synchronous machine power angle when the multi-machine system fault is removed according to the first synchronous machine power angle;

[0093] The third calculation module is used to calculate the second output phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed and the stable limit phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed according to the dynamic equation mathematical model and the second synchronous machine power angle;

[0094] The first region area calculation module is used to calculate the first region area according to the dynamic equation mathematical model, the second synchronous machine power angle, the first output phase angle and the second output phase angle; wherein the first region area is: the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 at the new energy end;

[0095] The second region area calculation module is used to calculate the second region area according to the dynamic equation mathematical model, the second synchronous machine power angle, the second output phase angle and the stable limit phase angle; wherein the second region area is: the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 end;

[0096] The stability evaluation module is used to determine the synchronization stability of the phase-locked loop of the new energy generator set according to the area of ​​the first region and the area of ​​the second region.

[0097] In this embodiment, the third calculation module includes: a second output phase angle calculation unit and a stability limit phase angle calculation unit;

[0098] The second output phase angle calculation unit is used to set i e Equal to i d , and substitute the power angle of the second synchronous unit before the multi-machine system failure into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculate the second output phase angle of the phase-locked loop at the new energy end before the multi-machine system failure;

[0099] The stability limit phase angle calculation unit is used to set i eIt is equal to the maximum value of the d-axis component of the output current of the new energy unit, and the power angle of the second synchronous 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 stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system failure is removed is calculated.

[0100] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system, characterized in that: include: According to 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; Calculate the first output phase angle of the phase-locked loop at the new energy end before the multi-machine system fails according to the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system fails; Calculating a second synchronous machine power angle when a multi-machine system fault is cleared according to the first synchronous machine power angle; Calculate the second output phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed and the stable limit phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed according to the dynamic equation mathematical model and the second synchronous machine power angle; The area of ​​the first region is calculated according to the dynamic equation mathematical model, the second synchronous machine power angle, the first output phase angle and the second output phase angle; wherein the area of ​​the first region is the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 at the new energy end; The area of ​​the second region is calculated according to the dynamic equation mathematical model, the second synchronous machine power angle, the second output phase angle and the stable limit phase angle; wherein the area of ​​the second region is the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 end; The synchronization stability of the phase-locked loop of the new energy generator set is determined according to the area of ​​the first region and the area of ​​the second region.

2. According to claim 1, a method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system is 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 Indicates the active power of new energy; U S Indicates infinite bus voltage; U d Represents the d-axis component of the voltage of the new energy unit; E G Represents the potential inside the synchronous unit; δ G Indicates the power angle of the synchronous unit; δ W Represents the output phase angle of the new energy phase-locked loop; i e Represents the node injection current of the new energy unit; i d Represents the d-axis component of the output current of the new energy unit.

3. According to claim 2, a method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system is characterized in that: The method of calculating the first output phase angle of the phase-locked loop at the new energy end before the multi-machine system fails according to the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system fails comprises: Let i e Equal to i d The power angle of the first synchronous 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 phase-locked loop at the new energy end before the multi-machine system failure is calculated.

4. According to claim 1, a method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system is characterized in that: The calculating, according to the first synchronous machine power angle, a second synchronous machine power angle when a multi-machine system fault is removed comprises: According to the first synchronous machine power angle, a second synchronous machine power angle when a multi-machine system fault is removed is calculated by a second synchronous machine power angle calculation formula; The calculation formula of the second synchronous machine power angle is as follows: δ GC Indicates the power angle of the second synchronous machine when the multi-machine system fails; δ G0 represents the first synchronous machine power angle; t represents the fault duration; Δt represents the preset step size; ω N Indicates the angular velocity of the synchronous machine's rotating shaft; T JG Indicates the inertia time constant of the synchronous machine; P T Indicates the mechanical power of the synchronous machine.

5. According to claim 2, a method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system is characterized in that: The method of calculating the second output phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed and the stable limit phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed according to the dynamic equation mathematical model and the second synchronous machine power angle includes: Let i e Equal to i d , and substitute the power angle of the second synchronous unit before the multi-machine system failure into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculate the second output phase angle of the phase-locked loop at the new energy end before the multi-machine system failure; Let i e It is equal to the maximum value of the d-axis component of the output current of the new energy unit, and the power angle of the second synchronous 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 stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system failure is removed is calculated.

6. The method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system according to claim 1 is characterized in that: The calculation of the area of ​​the first region satisfies the following calculation formula: Among them, δ W0 represents the first output phase angle; δ W1 represents the second output phase angle; represents the d-axis component of the output current of the new energy generator set at the second synchronous machine power angle; represents the node injection current of the new energy generator set at the second synchronous machine power angle; S ac It represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to when the new energy end phase-locked loop changes 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 end output current.

7. The method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system according to claim 1 is characterized in that: The calculation of the area of ​​the second region satisfies the following calculation formula: Among them, δ W1 represents the second output phase angle; δ Wcr represents the stable limiting phase angle; represents the d-axis component of the output current of the new energy generator set at the second synchronous machine power angle; represents the node injection current of the new energy generator set at the second synchronous machine power angle; S dc It represents the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to when the new energy end phase-locked loop changes 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 end output current.

8. The method for evaluating the synchronous stability of a phase-locked loop of a new energy generator set in a multi-machine system according to claim 1 is characterized in that: The determining of the synchronization stability of the phase-locked loop of the new energy generator set according to the area of ​​the first region and the area of ​​the second region includes: When the area of ​​the first region is larger than that of the second region, the phase-locked loop synchronization instability of the new energy unit occurs; When the area of ​​the first region is less than or equal to the area of ​​the second region, the phase-locked loop synchronization of the new energy unit is stable.

9. A phase-locked loop synchronization stability assessment system for new energy units in a multi-machine system, characterized in that: include: A dynamic equation mathematical model building 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; The dynamic equation mathematical model building module is used to build a dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop according to 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 end before the multi-machine system fails according to the dynamic equation mathematical model and the first synchronous machine power angle before the multi-machine system fails; The second calculation module is used to calculate the second synchronous machine power angle when the multi-machine system fault is removed according to 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 generator set when the multi-machine system fault is removed and the stable limit phase angle of the phase-locked loop of the new energy generator set when the multi-machine system fault is removed according to the dynamic equation mathematical model and the second synchronous machine power angle; The first region area calculation module is used to calculate the first region area according to the dynamic equation mathematical model, the second synchronous machine power angle, the first output phase angle and the second output phase angle; wherein the first region area is: the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 at the new energy end; The second region area calculation module is used to calculate the second region area according to the dynamic equation mathematical model, the second synchronous machine power angle, the second output phase angle and the stable limit phase angle; wherein the second region area is: the area enclosed by the phase-locked loop output phase angle characteristic curve corresponding to the change of the phase-locked loop at the new energy end 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 end; The stability evaluation module is used to determine the synchronization stability of the phase-locked loop of the new energy generator set according to the area of ​​the first region and the area of ​​the second region.

10. The phase-locked loop synchronous stability evaluation system for new energy units in a multi-machine system according to claim 9, characterized in that: The third calculation module includes: a second output phase angle calculation unit and a stability limit phase angle calculation unit; The second output phase angle calculation unit is used to e Equal to i d , and substitute the power angle of the second synchronous unit before the multi-machine system failure into the mathematical expression of the dynamic equation mathematical model of the output phase angle of the new energy phase-locked loop, and calculate the second output phase angle of the phase-locked loop at the new energy end before the multi-machine system failure; The stability limit phase angle calculation unit is used to set i e It is equal to the maximum value of the d-axis component of the output current of the new energy unit, and the power angle of the second synchronous 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 stable limit phase angle of the phase-locked loop of the new energy unit when the multi-machine system failure is removed is calculated.

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