Method, device, system and computer-readable medium for determining disturbance sources of wind farm subsynchronous oscillation based on energy function analysis

Abstract

The present invention provides a method, device, system, and computer-readable medium for determining the source of disturbances in wind farm subsynchronous oscillations based on energy function analysis. The method comprises: constructing a subsynchronous oscillation simulation model for a doubly-fed wind turbine; analyzing the performance characteristics of the subsynchronous oscillation mechanism of a wind power grid-connected system, determining different subsynchronous oscillation generation mechanisms and their influencing factors and degree of influence; constructing an energy function suitable for subsynchronous oscillations in wind power grid-connected systems; analyzing the oscillation characteristics of the wind turbine based on changes in internal oscillation energy; applying the wind turbine energy function to a multi-machine system containing wind turbines, and determining the main source of disturbances that generate subsynchronous oscillations after the system is disturbed based on the relevant energy changes. The present invention can apply the energy function method to the subsynchronous oscillation problem of wind turbines, conduct a more comprehensive and accurate stability analysis of the power system, and determine the main disturbance unit based on relevant information such as the start-up time, oscillation amplitude, and trend.

Description

Technical Field

[0001] The present invention relates to the technical field of modern large power grids, and in particular to energy analysis of subsynchronous oscillations in wind power grid-connected power systems, and more specifically to a method for determining disturbance sources of subsynchronous oscillations in wind farms based on energy function analysis. Background Art

[0002] In recent years, with the increasing use of electronic power in wind turbines and the resulting surge in investment in reactive power compensation and series compensation devices, subsynchronous oscillations (SSOs) have become a threat to power systems. SSOs are caused by unique electromechanical coupling in power systems, leading to oscillation instability. Severe cases can damage electrical equipment and cause serious accidents. Wind turbines are diverse in type and operating modes, and once SSOs occur, their oscillation characteristics vary significantly.

[0003] The application scope of traditional subsynchronous oscillation analysis and control methods is limited. Therefore, new analysis methods need to be introduced to solve the subsynchronous oscillation problem of wind turbines to achieve subsynchronous oscillation monitoring and suppression, and ensure the safe and stable operation of the power system. Summary of the Invention

[0004] Given that there are many types of wind turbines and their operating modes are also different, once subsynchronous oscillation problems occur, the oscillation characteristics they exhibit are also very different. The scope of application of traditional subsynchronous oscillation analysis and control methods is limited. In view of this, the present invention aims to propose a method for determining the source of disturbance of subsynchronous oscillation of wind farms based on energy function analysis. Based on the different generation mechanisms of synchronous oscillations and their influencing factors and influence degrees, an energy function suitable for subsynchronous oscillation of wind power grid-connected is constructed, and the energy function method is applied to the subsynchronous oscillation problem of wind turbines, so as to perform a more comprehensive and accurate stability analysis of the power system, and judge the main disturbance units based on relevant information such as the start-up time, oscillation amplitude and trend.

[0005] According to a first aspect of the present invention, a method for determining the disturbance source of subsynchronous oscillation of a wind farm based on energy function analysis is proposed, comprising the following steps:

[0006] Step 1: Based on the doubly-fed wind turbine model formed by the aggregation of doubly-fed wind turbines, a subsynchronous oscillation simulation model of the doubly-fed wind turbine is constructed;

[0007] Step 2: Analyze the time domain variation characteristics of relevant electrical quantities based on the doubly fed wind turbine infinite system to obtain the key influencing factors of IGE, SSCI and SSTI phenomena;

[0008] Step 3: Based on the key influencing factors of IGE, SSCI and SSTI oscillations, an energy function suitable for subsynchronous oscillation of wind power grid connection is constructed;

[0009] Step 4: Based on the energy function of the subsynchronous oscillation of wind power grid connection, the energy characteristics of different IGE, SSCI and SSTI are analyzed;

[0010] Step 5: Apply the constructed energy function of subsynchronous oscillation of wind power grid connection to a multi-machine system including a doubly fed wind turbine, analyze the oscillation energy characteristics based on multiple parameters of the oscillation energy, and determine the main disturbing unit.

[0011] As an optional embodiment, the subsynchronous oscillation simulation model of the doubly-fed wind turbine group is constructed based on the doubly-fed wind turbine group model formed by the aggregation of doubly-fed wind turbines, including:

[0012] On the basis of the doubly-fed wind turbine model composed of doubly-fed wind turbines, the voltage is boosted by a step-up transformer and then connected to a line with a controllable series compensation capacitor. Under the normal operation of the doubly-fed wind turbine model, the series compensation capacitor is put into operation according to the preset requirements to induce subsynchronous oscillation, and a subsynchronous oscillation simulation model of the doubly-fed wind turbine is constructed.

[0013] As an optional embodiment, the time domain variation characteristics of relevant electrical quantities are analyzed based on the doubly fed wind turbine infinite system to obtain the key influencing factors of IGE, SSCI and SSTI phenomena, including:

[0014] For IGE, series compensation and wind speed are identified as key influencing factors;

[0015] For SSCI, determine the k in the RSC control module p2 and k i2 is the key influencing factor;

[0016] Regarding SSTI, it is determined that SSTI is not the main subsynchronous oscillation of the doubly fed wind turbine generator system.

[0017] As an optional embodiment, based on the key influencing factors of IGE, SSCI and SSTI oscillations, energy functions suitable for subsynchronous oscillation of wind power grid connection and energy functions of the line are respectively constructed, that is, energy functions are constructed for static components. On this basis, energy characteristics of different IGE, SSCI and SSTI are analyzed, including:

[0018] Under the IGE mechanism, the DFIG will consume subsynchronous oscillation energy, and the series compensation capacitor will emit energy during the oscillation process. Therefore, when the DFIG is connected to the grid via the series compensation capacitor, if the subsynchronous energy emitted by the series compensation capacitor is greater than the subsynchronous energy consumed by the DFIG, it is determined that the DFIG grid-connected system emits subsynchronous oscillation energy, and the DFIG grid-connected system exhibits a negative damping state, that is, IGE oscillation occurs.

[0019] Moreover, the increase in the series compensation degree of the series compensation capacitor and the decrease in wind speed will increase the energy variation amplitude of the grid-connected system of the doubly-fed wind turbine, leading to the intensification of oscillation and the increase of non-periodic components, that is, the intensification of the IGE phenomenon.

[0020] Under the SSCI mechanism, the oscillation energy change of the RSC control module is characterized. When the key influencing factor k in the RSC control module p2 and k i2 As k increases, the amplitude of the oscillation energy increases, and k p2 changes have a greater impact on it.

[0021] In an optional embodiment, the energy function of the subsynchronous oscillation of wind power grid connection is applied to a multi-machine system including a doubly fed wind turbine, and the oscillation energy characteristics are analyzed according to multiple parameters of the oscillation energy to determine the main disturbing unit, including:

[0022] The constructed energy function of subsynchronous oscillation of wind power grid connection is applied to a multi-machine system including a doubly fed wind turbine. The thermal power unit adopts a multi-mass block model, and the transient energy in its components is expressed as follows:

[0023]

[0024] Where ΔW pi is the potential energy of the position of the i-th mass block; ΔW ki is the kinetic energy of the i-th mass block relative to the synchronous speed; ΔW ki,i+1 is the shaft energy generated by the speed difference between the i-th mass block and the i+1-th mass block;

[0025] Therefore, when the system experiences subsynchronous oscillation due to disturbance, the oscillation energy characteristics of each unit can be analyzed according to the starting time, oscillation amplitude and trend of the relevant oscillation energy to determine the main disturbing unit.

[0026] As an optional embodiment, when the system experiences subsynchronous oscillation due to disturbance, analyzing the oscillation energy characteristics of each unit based on the start time, oscillation amplitude and trend of the relevant oscillation energy to determine the main disturbing unit includes:

[0027] When the system disturbance causes the doubly-fed wind turbine to become a disturbing unit, it generates subsynchronous oscillations, which are transmitted to the thermal power unit and induce torsional vibration of the thermal power unit's shaft system;

[0028] If the disturbance near the outlet of the thermal power unit causes the thermal power unit to generate shaft torsional vibration, the subsynchronous component will be transmitted to the wind turbine, exacerbating the subsynchronous oscillation phenomenon of the wind turbine; if the subsynchronous component fails to cause serious torsional vibration of the thermal power unit, the wind turbine will serve as the main disturbance source and trigger long-term subsynchronous oscillation of the system.

[0029] According to a second aspect of the present invention, a device for determining a disturbance source of subsynchronous oscillation of a wind farm based on energy function analysis is proposed, comprising:

[0030] A model building module for building a subsynchronous oscillation simulation model of a doubly-fed wind turbine generator system based on a doubly-fed wind turbine generator system model formed by aggregation of doubly-fed wind turbines;

[0031] A key factor acquisition module for analyzing the time domain variation characteristics of relevant electrical quantities based on the doubly fed wind turbine infinite system and obtaining the key influencing factors of IGE, SSCI and SSTI phenomena;

[0032] An energy function building module for constructing an energy function for subsynchronous oscillations of wind power grid connection based on the key influencing factors of IGE, SSCI and SSTI oscillations;

[0033] Energy characteristics analysis module for analyzing the energy characteristics of different IGE, SSCI and SSTI based on the energy function of subsynchronous oscillation of wind power grid connection; and

[0034] A disturbance determination module is used to apply the constructed energy function of wind power grid-connected subsynchronous oscillation to a multi-machine system including doubly fed wind turbines, analyze the oscillation energy characteristics according to multiple parameters of the oscillation energy, and determine the disturbance of the main disturbance unit.

[0035] According to a third aspect of the present invention, a disturbance source determination system for subsynchronous oscillations of wind farms based on the characteristics of the subsynchronous oscillation mechanism of wind power grid connection is proposed, comprising: one or more processors; and a memory; the memory stores operable instructions, which, when executed by the one or more processors, enable the one or more processors to perform operations, and the operations include the method flow as described above.

[0036] According to a fourth aspect of the present invention, a computer-readable medium storing software is proposed, wherein the software includes instructions that can be executed by one or more computers, and the instructions, through such execution, enable the one or more computers to perform operations, and the operations include the method flow as described above.

[0037] The above scheme of the present invention proposes to construct an energy function suitable for the sub-synchronous oscillation of wind farms based on the performance characteristics of the relevant mechanism of sub-synchronous oscillation of wind power grid-connected power, and further realizes the method for determining the disturbance source of sub-synchronous oscillation of wind farms. Before constructing the energy function, a sub-synchronous oscillation simulation model of the doubly fed wind turbine is first established. The main components of the simulation model include wind turbines, transmission systems, induction generators, converters and control systems, etc. Based on this technology, an energy function module suitable for sub-synchronous oscillation of wind power grid-connected power is constructed, and its oscillation characteristics are analyzed according to the changes in the internal oscillation energy of the wind turbine. Finally, the wind turbine energy module is applied to a multi-machine system containing wind turbines, combined with time domain simulation, and the main disturbance source of sub-synchronous oscillation generated after the system is disturbed is determined according to the relevant energy changes.

[0038] It can be seen from the above technical solutions of the present invention that, compared with the prior art, the present invention has the following significant advantages:

[0039] 1. The method proposed in this paper overcomes the problem that the conventional subsynchronous oscillation analysis and control methods are limited in scope due to the wide variety of wind turbine types and operating modes. This problem is that once subsynchronous oscillation occurs, the oscillation characteristics exhibited vary greatly. By comparing and analyzing the amplitude and phase data of the oscillation energy of relevant modules, the disturbing units and the disturbed units in the wind farm can be identified.

[0040] 2. The method proposed in the present invention applies the energy function method to a multi-machine system including wind power and thermal power units. For the wind-fire combined transmission system, the subsynchronous oscillation energy characteristics are studied through the changes in the relevant energy on the outlet side and inside the wind power units and thermal power units. The main disturbing unit can be judged based on relevant information such as the starting time, oscillation amplitude and trend.

[0041] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below, as long as such concepts are not mutually inconsistent, can be considered part of the inventive subject matter of this disclosure. In addition, all combinations of the claimed subject matter are considered part of the inventive subject matter of this disclosure.

[0042] The foregoing and other aspects, embodiments, and features of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the present invention, such as features and / or beneficial effects of the exemplary embodiments, will become apparent from the following description or through practice of specific embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings are not intended to be drawn to scale. In the accompanying drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For clarity, not every component is labeled in every figure. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings.

[0044] Figure 1 It is a flow chart of a method for determining a disturbance source of a wind farm sub-synchronous oscillation based on energy function analysis according to an embodiment of the present invention.

[0045] Figure 2 1 is an example diagram illustrating the change of system energy during subsynchronous oscillation according to certain embodiments of the present invention, wherein (a) is a curve showing the change of system energy over time when the series compensation degree is 30% under the IGE mechanism, and (b) is a curve showing the change of system energy over time when the series compensation degree is 50% under the IGE mechanism.

[0046] Figure 3 Another example diagram illustrates system energy changes during subsynchronous oscillation according to certain embodiments of the present invention. (a) shows the system energy change over time when the wind speed is 9 m / s under the IGE mechanism, and (b) shows the system energy change over time when the wind speed is 15 m / s under the IGE mechanism.

[0047] Figure 4 is another example diagram illustrating the energy change of the system during subsynchronous oscillation according to some embodiments of the present invention, which is different k under the SSCI mechanism. p2 Curve of converter module energy changing with time.

[0048] Figure 5 is another example diagram illustrating the energy change of the system during subsynchronous oscillation according to some embodiments of the present invention, which is different k under the SSCI mechanism. i2 Curve of converter module energy changing with time. DETAILED DESCRIPTION

[0049] In order to better understand the technical content of the present invention, specific embodiments are given and described below with reference to the accompanying drawings.

[0050] Various aspects of the present invention are described in this disclosure with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. The embodiments of the present disclosure are not necessarily intended to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed herein are not limited to any embodiment. In addition, some aspects of the present disclosure may be used alone or in any appropriate combination with other aspects disclosed herein.

[0051] Combine Figure 1 The example process of the embodiment of the present invention is a method for determining the source of disturbance of sub-synchronous oscillation of wind farms based on energy function analysis. Based on the performance characteristics of the relevant mechanism of sub-synchronous oscillation of wind power grid connection, an energy function method suitable for sub-synchronous oscillation of wind farms is constructed. The energy function method is applied to the sub-synchronous oscillation problem of wind turbines, and the stability analysis of the power system is carried out more comprehensively and accurately. According to the relevant information such as the starting time, oscillation amplitude and trend, the main disturbance unit is judged.

[0052] As an optional embodiment, the method for determining the disturbance source of wind farm subsynchronous oscillation based on energy function analysis is implemented, and the process includes the following steps:

[0053] Step 1: Based on the doubly-fed wind turbine model formed by the aggregation of doubly-fed wind turbines, a subsynchronous oscillation simulation model of the doubly-fed wind turbine is constructed;

[0054] Step 2: Analyze the time domain variation characteristics of relevant electrical quantities based on the doubly fed wind turbine infinite system to obtain the key influencing factors of IGE, SSCI and SSTI phenomena;

[0055] Step 3: Based on the key influencing factors of IGE, SSCI and SSTI oscillations, an energy function suitable for subsynchronous oscillation of wind power grid connection is constructed;

[0056] Step 4: Based on the energy function of the subsynchronous oscillation of wind power grid connection, the energy characteristics of different IGE, SSCI and SSTI are analyzed;

[0057] Step 5: Apply the constructed energy function of subsynchronous oscillation of wind power grid connection to a multi-machine system including a doubly fed wind turbine, analyze the oscillation energy characteristics based on multiple parameters of the oscillation energy, and determine the main disturbing unit.

[0058]

Establishment of subsynchronous oscillation simulation model

[0059] In an optional embodiment, in the aforementioned step 1, based on a doubly-fed wind turbine model formed by aggregation of doubly-fed wind turbines, the voltage is boosted by a step-up transformer and then connected to a line with a controllable series compensation capacitor. Under normal operation of the doubly-fed wind turbine model, the series compensation capacitor is put into operation according to preset requirements to induce subsynchronous oscillation, thereby constructing a subsynchronous oscillation simulation model of the doubly-fed wind turbine.

[0060] In the example of the present invention, a wind turbine model composed of multiple 15KW doubly fed wind turbines (50 units as an example) is constructed in MATLAB / simulink. Its main components include wind turbines, transmission systems, induction generators, converters and control systems.

[0061] In different scenarios or simulations, the wind turbine model can be adjusted according to the needs or set operating modes and scenarios.

[0062] In the example of the present invention, a wind turbine model is constructed, which is connected to a line with a controllable series compensation capacitor after being boosted by a step-up transformer. When the wind power system is operating normally, the series compensation capacitor is put into operation according to the set requirements, causing subsynchronous oscillation.

[0063]

Oscillation characteristics of different mechanisms

[0064] In an optional embodiment, in the aforementioned step 2, the time domain variation characteristics of relevant electrical quantities are analyzed based on the doubly fed wind turbine infinite system to obtain the key influencing factors of the IGE, SSCI and SSTI phenomena, including:

[0065] For IGE, series compensation and wind speed are identified as key influencing factors;

[0066] For SSCI, determine the k in the RSC control module p2 and k i2 is the key influencing factor;

[0067] Regarding SSTI, it is determined that SSTI is not the main subsynchronous oscillation of the doubly fed wind turbine generator system.

[0068] It should be understood that in step 2 of the present invention, a doubly-fed wind turbine infinite system can be used to analyze the time domain variation characteristics of relevant electrical quantities in subsynchronous oscillations, and the mechanisms and oscillation characteristics of IGE, SSCI, and SSTI are analyzed respectively. Based on the results, the following conclusions are drawn:

[0069] Regarding the IGE phenomenon, both theoretical analysis and simulation verification have shown that series compensation and wind speed are the key influencing factors. The greater the series compensation and the smaller the wind speed, the more obvious the IGE phenomenon.

[0070] In response to the SSCI phenomenon, the k p2 and k i2 All of them will affect the oscillation. According to the simulation, k p2 and k i2 The increase of k p2 The impact is greater;

[0071] Regarding the SSTI phenomenon, it was found that when the wind power grid-connected system is operating normally, the series compensation degree is difficult to reach the required value to produce the SSTI phenomenon. Therefore, the SSTI phenomenon is not the main subsynchronous oscillation problem of the doubly fed wind turbine generator set.

[0072]

Energy function construction

[0073] In an example of the present invention, when a sudden change in the relative power angle of the observed unit is detected, an energy function suitable for the subsynchronous oscillation of the wind turbine is constructed based on models such as the induction generator, converter control, and series compensation capacitor, to facilitate subsequent analysis and judgment processing.

[0074] Compared to low-frequency oscillations, subsynchronous oscillations have higher frequencies, less clearly defined power, and various power-frequency phasor representations cannot be directly used. Consequently, the energy function formulas developed for analyzing low-frequency oscillations cannot be directly applied to subsynchronous oscillation analysis. Therefore, in step 3 above, an innovative approach was used to construct the energy function for the doubly-fed wind turbine for subsynchronous oscillation analysis.

[0075] In an optional embodiment, an energy function suitable for subsynchronous oscillation of wind power grid connection is constructed based on key influencing factors of IGE, SSCI and SSTI oscillations.

[0076] 3.1. Construct the energy function for subsynchronous oscillation of wind power grid connection as follows:

[0077]

[0078] In formula (1), U x 、U y are the x-axis and y-axis components of the voltage at the fan outlet side; I x , I y are the x-axis and y-axis components of the current at the fan outlet side; U d 、U q are the d-axis and q-axis components of the voltage at the fan outlet side respectively; I d , I q are the d-axis and q-axis components of the current at the fan outlet side respectively; P e is the output active power; θ is the phase-locked angle of the wind turbine phase-locked loop.

[0079] When a doubly fed wind turbine contains multiple oscillation modes, the components on the dq axes become the superposition of oscillation components of multiple frequencies. Generally, filtering can be used to extract components at different frequencies, and the corresponding energy functions can be calculated to obtain the oscillation characteristics under different modes.

[0080] According to the above formula (12), the output energy of the generator is divided into two parts and obtained separately, namely:

[0081] W1=∫P e dθ (13)

[0082] W2=∫I d dU q -∫I q dU d (14)

[0083] Among them, the equivalent calculation of oscillation energy W1 is:

[0084] Known:

[0085]

[0086] Among them, P m is the mechanical power in the system; P em is the electromagnetic power transmitted from the rotor to the stator through the gap; T t is the inertia time constant of the wind turbine; T m is the mechanical torque of the wind turbine; T g is the inertia time constant of the generator; ω t is the speed of the wind turbine converted to the high-speed side of the gearbox; ω r is the rotor speed; K sh is the strength coefficient of the transmission shaft; θ tw is the twist angle of the transmission shaft; D sh is the damping coefficient.

[0087] Substituting formula (4) into formula (2), we get:

[0088]

[0089] In formula (16), the first part ∫P m dδ is the position potential energy of the fan, part 2 is the change in kinetic energy of the shaft system between the wind turbine and the generator, the third part is the kinetic energy change of each mass block of the wind turbine and generator, the fourth part D∫ω i 2 dt is the energy consumed by damping, which is the dissipation term.

[0090] In a doubly fed wind turbine, the grid-side converter's control parameters have little impact on subsynchronous oscillations, and the energy provided by the GSC in subsynchronous oscillation mode is negligible. However, the RSC provides energy to the generator by providing excitation current, which is then transferred to the grid via the stator.

[0091] According to the stator and rotor voltage equations and the magnetic flux equation, the oscillation energy W2 can be obtained:

[0092]

[0093] Among them, i ds 、i qs are the d-axis and q-axis components of the stator current; u ds 、u qs are the d-axis and q-axis components of the terminal voltage; L r , L s are the stator and rotor inductances respectively; Lm is the mutual inductance between stator and rotor; ω r is the rotor speed; ω s is the synchronous speed of the generator; i dr 、i qr are the d-axis and q-axis components of the rotor current; R r is the rotor resistance.

[0094] It can be seen that the oscillation energy W2 is composed of the potential energy stored inside the generator after the rotating magnetic field is established, the energy dissipated by the rotor winding, and the excitation-related potential energy. When the doubly fed wind turbine is operating normally, u qs and u ds are all constants, and W2 in the above formula is zero. Therefore, under subsynchronous oscillation, the relevant problems can be analyzed by the energy changes on the converter side.

[0095] The occurrence of subsynchronous oscillation in a wind power grid-connected system will not only affect the internal structure of the doubly fed wind turbine, but also cause oscillations and energy changes in the line. Therefore, an energy function of the line, that is, an energy function of the static elements, can be constructed for subsequent analysis.

[0096] 3.2. Construct the energy function of the circuit, that is, construct the energy function for the static components;

[0097] The mathematical model of the series compensation element, i.e. the series compensation capacitor, is as follows:

[0098]

[0099] Where u c is the voltage amplitude of the capacitor grid-connected side; u cd 、u cq The d-axis and q-axis components of its voltage; i c is the capacitor current; ω e is the reference angular velocity; ω1 is the angular velocity of rotation of the dq coordinate system.

[0100] The energy function W3 of the compensation element is constructed as follows:

[0101]

[0102] Among them, u cd 、u cq are the d-axis and q-axis components of the capacitor voltage; i cd 、i cq are the d-axis and q-axis components of the capacitor current; ω s is the synchronous speed of the generator; ω1 is the angular velocity of rotation of the dq coordinate system.

[0103] It can be seen that the first two terms of the energy function of the element are the interaction energy between the wind turbine and the series compensation, and the third term is the damping energy, which is related to the integration path.

[0104]

Oscillation energy analysis under different mechanisms

[0105] In an optional embodiment, in the aforementioned step 4, based on the energy function of the subsynchronous oscillation of wind power grid connection, analyzing the energy characteristics of different IGE, SSCI and SSTI includes:

[0106] Under the IGE mechanism, the DFIG will consume subsynchronous oscillation energy, and the series compensation capacitor will emit energy during the oscillation process. Therefore, when the DFIG is connected to the grid via the series compensation capacitor, if the subsynchronous energy emitted by the series compensation capacitor is greater than the subsynchronous energy consumed by the DFIG, it is determined that the DFIG grid-connected system emits subsynchronous oscillation energy, and the DFIG grid-connected system exhibits a negative damping state, that is, IGE oscillation occurs.

[0107] Moreover, the effects of series compensation and wind speed on IGE phenomenon can also be reflected in the oscillation energy. Figure 2 、 3 As shown in the figure, the increase of series compensation degree of series compensation capacitor and the decrease of wind speed will increase the energy variation amplitude of the grid-connected system of doubly-fed wind turbines, leading to the intensification of oscillation and the increase of non-periodic components, that is, the IGE phenomenon is intensified.

[0108] Under the SSCI mechanism, the oscillation energy change of the RSC control module is characterized. When the key influencing factor k in the RSC control module p2 and k i2 As k increases, the amplitude of the oscillation energy increases, and k p2 The changes in Figure 4 、 5 As shown, with k i2 、k p2 As the value of k increases, the amplitude of the oscillation energy also increases. p2 changes have a greater impact on it.

[0109] Among them, k p2 is the proportional coefficient of the current inner loop control, k i2 is the integral coefficient of the current inner loop control.

[0110]

Analysis of internal oscillation energy characteristics of wind farms

[0111] A dual-machine system is adopted, which is composed of two doubly fed wind turbines. By changing the position of the series compensation capacitor, the system produces subsynchronous oscillations. Its oscillation characteristics are analyzed through time domain simulation and energy change. It can be seen that the oscillation energy amplitude of the oscillation source is higher than that of other units. The larger the capacity of the oscillation source unit, the greater the impact on other units in the wind farm.

[0112] Therefore, in the wind farm grid-connected system, if a disturbance source occurs and triggers subsynchronous oscillation, the oscillation source can be determined based on the total energy and internal kinetic energy oscillation changes of the wind turbines. According to the energy interaction between wind turbines, all wind turbines in the wind farm are divided into disturbing wind turbines and disturbed wind turbines, and subsynchronous oscillation analysis is performed.

[0113]

Analysis of Oscillation Energy Characteristics of Multi-machine System

[0114] In an optional embodiment, in the aforementioned step 5, the constructed energy function of the subsynchronous oscillation of wind power grid connection is applied to a multi-machine system including a doubly fed wind turbine, wherein the thermal power unit adopts a multi-mass block model, and the transient energy in its components is expressed as follows:

[0115]

[0116] Where ΔW pi is the potential energy of the position of the i-th mass block; ΔW ki is the kinetic energy of the i-th mass block relative to the synchronous speed; ΔW ki,i+1 is the shaft energy generated by the speed difference between the i-th mass block and the i+1-th mass block; M i is the inertia time constant of the rotor; K i,i+1 is the elastic constant between adjacent masses.

[0117] Therefore, when the system experiences subsynchronous oscillation due to disturbance, the oscillation energy characteristics of each unit can be analyzed according to the starting time, oscillation amplitude and trend of the relevant oscillation energy to determine the main disturbing unit.

[0118] In a further example, when the system experiences subsynchronous oscillation due to disturbance, the oscillation energy characteristics of each unit are analyzed based on the start time, oscillation amplitude and trend of the relevant oscillation energy to determine the main disturbing unit, including:

[0119] When the system disturbance causes the doubly-fed wind turbine to become a disturbing unit, it generates subsynchronous oscillations, which are transmitted to the thermal power unit and induce torsional vibration of the thermal power unit's shaft system;

[0120] If the disturbance near the outlet of the thermal power unit causes the thermal power unit to generate shaft torsional vibration, the subsynchronous component will be transmitted to the wind turbine, exacerbating the subsynchronous oscillation phenomenon of the wind turbine; if the subsynchronous component fails to cause serious torsional vibration of the thermal power unit, the wind turbine will serve as the main disturbance source and trigger long-term subsynchronous oscillation of the system.

[0121]

Disturbance source determination device for wind farm subsynchronous oscillation

[0122] According to the above embodiments, the present invention further proposes a disturbance source determination device for wind farm subsynchronous oscillation based on energy function analysis, comprising:

[0123] A model building module for building a subsynchronous oscillation simulation model of a doubly-fed wind turbine generator system based on a doubly-fed wind turbine generator system model formed by aggregation of doubly-fed wind turbines;

[0124] A key factor acquisition module for analyzing the time domain variation characteristics of relevant electrical quantities based on the doubly fed wind turbine infinite system and obtaining the key influencing factors of IGE, SSCI and SSTI phenomena;

[0125] An energy function building module for constructing an energy function for subsynchronous oscillations of wind power grid connection based on the key influencing factors of IGE, SSCI and SSTI oscillations;

[0126] Energy characteristics analysis module for analyzing the energy characteristics of different IGE, SSCI and SSTI based on the energy function of subsynchronous oscillation of wind power grid connection; and

[0127] A disturbance determination module is used to apply the constructed energy function of wind power grid-connected subsynchronous oscillation to a multi-machine system including doubly fed wind turbines, analyze the oscillation energy characteristics according to multiple parameters of the oscillation energy, and determine the disturbance of the main disturbance unit.

[0128]

Disturbance source determination system for wind farm synchronous oscillation

[0129] Based on the above embodiments, the present invention further provides a system for determining the source of subsynchronous oscillation in a wind farm based on the characteristics of the subsynchronous oscillation mechanism of wind power grid connection, comprising: one or more processors and a memory. The memory is used to store operable instructions that, when executed by the one or more processors, cause the one or more processors to perform operations, including the process of the method described in the above embodiments.

[0130]

Computer readable medium

[0131] According to the above embodiments, the present invention also proposes a computer-readable medium for storing software, wherein the software includes instructions that can be executed by one or more computers, and the instructions enable the one or more computers to perform operations through such execution, and the operations include the process of the method as described in the above embodiments.

[0132] Therefore, the implementation of one or more of the aforementioned embodiments of the present invention, by applying the energy function analysis method to the subsynchronous oscillation analysis of the wind power grid-connected power system, can overcome the defect of limited application scope of traditional subsynchronous oscillation analysis and control methods. The method of the present invention can perform a more comprehensive and accurate stability analysis of the power system, and judge the main disturbance units based on relevant information such as the start-up time, oscillation amplitude and trend.

[0133] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for determining the disturbance source of wind farm subsynchronous oscillation based on energy function analysis, characterized in that: The following steps are involved: Step 1: Based on the doubly-fed wind turbine model formed by the aggregation of doubly-fed wind turbines, a subsynchronous oscillation simulation model of the doubly-fed wind turbine is constructed; Step 2: Analyze the time domain variation characteristics of relevant electrical quantities based on the doubly fed wind turbine infinite system to obtain the key influencing factors of IGE, SSCI and SSTI phenomena; Step 3: Based on the key influencing factors of IGE, SSCI and SSTI oscillations, an energy function suitable for subsynchronous oscillation of wind power grid connection is constructed; Step 4: Based on the energy function of the subsynchronous oscillation of wind power grid connection, the energy characteristics of different IGE, SSCI and SSTI are analyzed; Step 5: Apply the constructed energy function of the subsynchronous oscillation of wind power grid connection to a multi-machine system including a doubly fed wind turbine, analyze the oscillation energy characteristics based on multiple parameters of the oscillation energy, and determine the main disturbing unit; In step 3, the energy function applicable to subsynchronous oscillation of wind power grid connection is constructed based on the key influencing factors of IGE, SSCI and SSTI oscillations, including: Step 3.1: Construct the energy function for subsynchronous oscillation of wind power grid connection as follows: In formula (1), U d 、U q are the d-axis and q-axis components of the voltage at the fan outlet side respectively; I d , I q are the d-axis and q-axis components of the current at the fan outlet side respectively; P e is the output active power; θ is the phase-locked angle of the wind turbine phase-locked loop; According to the above formula (1), the output energy of the generator is divided into two parts and obtained separately, namely: W1=∫P e dθ (2) W2=∫I d you q -∫I q you d (3) Among them, the equivalent calculation of oscillation energy W1 is: Known: Substituting formula (4) into formula (2), we get: In formula (2), the first part ∫P m dδ is the position potential energy of the fan, part 2 is the change in kinetic energy of the shaft system between the wind turbine and the generator, the third part is the kinetic energy change of each mass block of the wind turbine and generator, the fourth part Energy is consumed for damping, and this part is the dissipation term; Among them, the equivalent calculation of oscillation energy W2 is: According to the stator and rotor voltage equations and magnetic flux equations, we can get: The oscillation energy W2 is composed of the potential energy stored inside the generator after the rotating magnetic field is established, the energy dissipated by the rotor winding, and the excitation-related potential energy. When the doubly fed wind turbine is operating normally, u qs and u ds are all constants, and W2 in the above formula is zero; Step 3.2: Construct the energy function of the circuit, that is, construct the energy function for the static components; The mathematical model of the series compensation element, i.e. the series compensation capacitor, is as follows: Where u c is the voltage amplitude of the capacitor grid-connected side; u cd 、u cq are the d-axis and q-axis components of its voltage; The energy function W3 of the compensation element is constructed as follows: Where i cd 、i cq are the d-axis and q-axis components of the capacitor current; u cd 、u cq are the d-axis and q-axis components of the capacitor side voltage; ω s is the synchronous speed of the motor.

2. The method for determining the disturbance source of wind farm subsynchronous oscillation based on energy function analysis according to claim 1 is characterized in that: Based on the doubly-fed wind turbine group model formed by the aggregation of doubly-fed wind turbines, a subsynchronous oscillation simulation model of the doubly-fed wind turbine group is constructed, including: On the basis of the doubly-fed wind turbine model composed of doubly-fed wind turbines, the voltage is boosted by a step-up transformer and then connected to a line with a controllable series compensation capacitor. Under the normal operation of the doubly-fed wind turbine model, the series compensation capacitor is put into operation according to the preset requirements to induce subsynchronous oscillation, and a subsynchronous oscillation simulation model of the doubly-fed wind turbine is constructed.

3. The method for determining the disturbance source of wind farm subsynchronous oscillation based on energy function analysis according to claim 1 is characterized in that: The time domain variation characteristics of relevant electrical quantities are analyzed based on the doubly fed wind turbine infinite system, and the key influencing factors of IGE, SSCI and SSTI phenomena are obtained, including: For IGE, series compensation and wind speed are identified as key influencing factors; For SSCI, determine the k in the RSC control module p2 and k i2 is the key influencing factor; Regarding SSTI, it is determined that SSTI is not the main subsynchronous oscillation of the doubly fed wind turbine generator system.

4. The method for determining the disturbance source of wind farm subsynchronous oscillation based on energy function analysis according to claim 1 is characterized in that: Based on the energy function of subsynchronous oscillation of wind power grid connection, the energy characteristics of different IGE, SSCI and SSTI are analyzed, including: Under the IGE mechanism, the DFIG will consume subsynchronous oscillation energy, and the series compensation capacitor will emit energy during the oscillation process. Therefore, when the DFIG is connected to the grid via the series compensation capacitor, if the subsynchronous energy emitted by the series compensation capacitor is greater than the subsynchronous energy consumed by the DFIG, it is determined that the DFIG grid-connected system emits subsynchronous oscillation energy, and the DFIG grid-connected system exhibits a negative damping state, that is, IGE oscillation occurs. Moreover, the increase in the series compensation degree of the series compensation capacitor and the decrease in wind speed will increase the energy variation amplitude of the grid-connected system of the doubly-fed wind turbine, leading to the intensification of oscillation and the increase of non-periodic components, that is, the intensification of the IGE phenomenon. Under the SSCI mechanism, the oscillation energy change of the RSC control module is characterized. When the key influencing factor k in the RSC control module p2 and k i2 As k increases, the amplitude of the oscillation energy increases, and k p2 changes have a greater impact on it.

5. The method for determining the disturbance source of wind farm subsynchronous oscillation based on energy function analysis according to claim 1, characterized in that: The energy function of the subsynchronous oscillation of wind power grid connection is applied to a multi-machine system including a doubly fed wind turbine, and the oscillation energy characteristics are analyzed according to multiple parameters of the oscillation energy to determine the main disturbing unit, including: The constructed energy function of subsynchronous oscillation of wind power grid connection is applied to a multi-machine system including a doubly fed wind turbine. The thermal power unit adopts a multi-mass block model, and the transient energy in its components is expressed as follows: Where △W pi is the potential energy of the position of the i-th mass block; △W ki is the kinetic energy of the i-th mass block relative to the synchronous speed; △W ki,i+1 is the shaft energy generated by the speed difference between the i-th mass block and the i+1-th mass block; Therefore, when the system experiences subsynchronous oscillation due to disturbance, the oscillation energy characteristics of each unit can be analyzed according to the starting time, oscillation amplitude and trend of the relevant oscillation energy to determine the main disturbing unit.

6. The method for determining disturbance sources of wind farm subsynchronous oscillations based on energy function analysis according to claim 5, characterized in that: When the system experiences subsynchronous oscillation due to disturbance, the oscillation energy characteristics of each unit are analyzed based on the start time, oscillation amplitude and trend of the relevant oscillation energy to determine the main disturbing unit, including: When the system disturbance causes the doubly-fed wind turbine to become a disturbing unit, it generates subsynchronous oscillations, which are transmitted to the thermal power unit and induce torsional vibration of the thermal power unit's shaft system; If the disturbance near the outlet of the thermal power unit causes the thermal power unit to generate shaft torsional vibration, the subsynchronous component will be transmitted to the wind turbine, exacerbating the subsynchronous oscillation phenomenon of the wind turbine; if the subsynchronous component fails to cause serious torsional vibration of the thermal power unit, the wind turbine will serve as the main disturbance source and trigger long-term subsynchronous oscillation of the system.

7. A device for determining disturbance sources of wind farm subsynchronous oscillations based on energy function analysis, characterized in that: include: A model building module for building a subsynchronous oscillation simulation model of a doubly-fed wind turbine generator system based on a doubly-fed wind turbine generator system model formed by aggregation of doubly-fed wind turbines; A key factor acquisition module for analyzing the time domain variation characteristics of relevant electrical quantities based on the doubly fed wind turbine infinite system and obtaining the key influencing factors of IGE, SSCI and SSTI phenomena; An energy function building module for constructing an energy function for subsynchronous oscillations of wind power grid connection based on the key influencing factors of IGE, SSCI and SSTI oscillations; Energy characteristics analysis module for analyzing the energy characteristics of different IGE, SSCI and SSTI based on the energy function of subsynchronous oscillation of wind power grid connection; as well as A disturbance determination module is used to apply the constructed energy function of wind power grid-connected subsynchronous oscillation to a multi-machine system including doubly fed wind turbines, analyze the oscillation energy characteristics based on multiple parameters of the oscillation energy, and determine the main disturbance unit; The energy function construction module is configured to construct an energy function suitable for subsynchronous oscillation of wind power grid connection according to the following process: Step 3.1: Construct the energy function for subsynchronous oscillation of wind power grid connection as follows: In formula (1), U d 、U q are the d-axis and q-axis components of the voltage at the fan outlet side respectively; I d , I q are the d-axis and q-axis components of the current at the fan outlet side respectively; P e is the output active power; θ is the phase-locked angle of the wind turbine phase-locked loop; According to the above formula (3), the output energy of the generator is divided into two parts and obtained separately, namely: W1=∫P e dθ (2) W2=∫I d you q -∫I q you d (3) Among them, the equivalent calculation of oscillation energy W1 is: Known: Substituting formula (4) into formula (2), we get: In formula (4), the first part ∫P m dδ is the position potential energy of the fan, part 2 is the change in kinetic energy of the shaft system between the wind turbine and the generator, the third part is the kinetic energy change of each mass block of the wind turbine and generator, the fourth part Energy is consumed for damping, and this part is the dissipation term; Among them, the equivalent calculation of oscillation energy W2 is: According to the stator and rotor voltage equations and magnetic flux equations, we can get: The oscillation energy W2 is composed of the potential energy stored inside the generator after the rotating magnetic field is established, the energy dissipated by the rotor winding, and the excitation-related potential energy. When the doubly fed wind turbine is operating normally, u qs and u ds are all constants, and W2 in the above formula is zero; Step 3.2: Construct the energy function of the circuit, that is, construct the energy function for the static components; The mathematical model of the series compensation element, i.e. the series compensation capacitor, is as follows: Where u c is the voltage amplitude of the capacitor grid-connected side; u cd 、u cq are the d-axis and q-axis components of its voltage; The energy function W3 of the compensation element is constructed as follows: Where i cd 、i cq are the d-axis and q-axis components of the capacitor current; u cd 、u cq are the d-axis and q-axis components of the capacitor side voltage; ω s is the synchronous speed of the motor.

8. A system for determining the source of disturbance of wind farm subsynchronous oscillation based on the characteristics of wind farm grid-connected subsynchronous oscillation mechanism, characterized by: include: one or more processors; A memory storing operable instructions, wherein when the instructions are executed by the one or more processors, the one or more processors are caused to perform operations, wherein the operations include the process of the method according to any one of claims 1 to 6.

9. A computer-readable medium storing software, characterized in that: The software includes instructions that can be executed by one or more computers, and the instructions, through such execution, enable the one or more computers to perform operations, wherein the operations include the process of the method according to any one of claims 1 to 6.

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