CN116626433A - Subsynchronous oscillation identification method based on measurement waveform - Google Patents

Subsynchronous oscillation identification method based on measurement waveform Download PDF

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CN116626433A
CN116626433A CN202310920713.9A CN202310920713A CN116626433A CN 116626433 A CN116626433 A CN 116626433A CN 202310920713 A CN202310920713 A CN 202310920713A CN 116626433 A CN116626433 A CN 116626433A
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voltage
time domain
transmission line
current
subsynchronous
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CN116626433B (en
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高波
刘平平
韩建
李泽文
邓芳明
韦宝泉
曾晗
于小四
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East China Jiaotong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Measuring Frequencies, Analyzing Spectra (AREA)

Abstract

The invention provides a subsynchronous oscillation identification method based on a measurement waveform, which comprises the following steps: step 1, measuring time domain voltages at two ends of a transmission line and time domain currents on the transmission line; step 2, calculating the voltage difference between two ends of the transmission line according to the time domain voltages between two ends of the transmission line obtained by measuring in the step 1, and constructing an expression of the voltage difference between two ends of the transmission line according to the series compensation system and the time domain current on the transmission line; step 3, obtaining the current time shift and impedance by measuring, and calculating auxiliary voltage drop according to the current time shift and the impedance; step 4, obtaining a voltage waveform only comprising a subsynchronous oscillation component according to the voltage difference between two ends of the transmission line and the auxiliary voltage drop; and step 5, extracting the frequency, damping ratio and amplitude of the subsynchronous oscillation according to the voltage waveform obtained in the step 4, and realizing the identification of the subsynchronous oscillation. The invention can solve the problem that the prior art lacks an effective method for identifying the subsynchronous oscillation.

Description

Subsynchronous oscillation identification method based on measurement waveform
Technical Field
The invention relates to the technical field of power grids, in particular to a subsynchronous oscillation identification method based on a measurement waveform.
Background
Wind energy is widely popularized and applied as a new energy source, however, when a wind farm is connected to a series compensation network, unstable subsynchronous oscillation (subsynchronous resonance, abbreviated as SSR) exists, the SSR can cause a great deal of electric energy loss of the power plant, and a great deal of wind turbine generators can be destroyed when serious. SSR is highly likely to occur even during normal operation.
Therefore, there is a need to identify the subsynchronous oscillation, which is mainly to calculate the frequency, damping ratio and amplitude of the subsynchronous oscillation, but the prior art lacks an efficient method for identifying the subsynchronous oscillation at an early stage.
Disclosure of Invention
The invention aims to provide a subsynchronous oscillation identification method based on a measurement waveform, which aims to solve the problem that the prior art lacks an effective method for identifying subsynchronous oscillation.
A method of subsynchronous oscillation identification based on a measured waveform, comprising:
step 1, measuring time domain voltages at two ends of a transmission line and time domain currents on the transmission line;
step 2, calculating the voltage difference between two ends of the transmission line according to the time domain voltages between two ends of the transmission line obtained by measuring in the step 1, and constructing an expression of the voltage difference between two ends of the transmission line according to the series compensation system and the time domain current on the transmission line;
step 3, obtaining the current time shift and impedance by measuring, and calculating auxiliary voltage drop according to the current time shift and the impedance;
step 4, obtaining a voltage waveform only comprising a subsynchronous oscillation component according to the voltage difference between two ends of the transmission line and the auxiliary voltage drop;
and step 5, extracting the frequency, damping ratio and amplitude of the subsynchronous oscillation according to the voltage waveform obtained in the step 4, and realizing the identification of the subsynchronous oscillation.
According to the method for identifying the subsynchronous oscillation based on the measured waveform, the expression of the voltage difference at two ends of the transmission line is constructed according to the series compensation system and the time domain current on the transmission line, the current time shift size and the impedance are obtained through measurement, the auxiliary voltage drop is calculated according to the current time shift size and the impedance, a voltage waveform only comprising the subsynchronous oscillation component is obtained, and finally the frequency, the damping ratio and the amplitude of the subsynchronous oscillation are extracted through the obtained voltage waveform, so that the identification of the subsynchronous oscillation is realized.
Drawings
Fig. 1 is a flowchart of a method for identifying sub-synchronous oscillation based on a measurement waveform according to an embodiment.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, a method for identifying subsynchronous oscillation based on measurement waveforms includes steps 1 to 5:
step 1, measuring time domain voltage at two ends of a transmission line and time domain current on the transmission line.
In step 1, the time domain voltages at two ends of the transmission line are respectively the first time domain voltagesV 1 And a second time domain voltageV 2 And a time-domain current on a transmission lineI 1 Can be directly measured. In addition, the time domain voltage across the transmission line and the time domain current on the transmission line also satisfy the following conditional expression:
wherein ,V 10 is a first time domain voltageV 1 Is used for the matching of the fundamental frequency component of (c),V 1ω is a first time domain voltageV 1 Is used to determine the sub-synchronous oscillation component of the (c),V 20 is the second time domain voltageV 2 Is used for the matching of the fundamental frequency component of (c),V 2ω is the second time domain voltageV 2 Is used to determine the sub-synchronous oscillation component of the (c),I 10 is a time domain currentI 1 Is used for the matching of the fundamental frequency component of (c),I 1ω is a time domain currentI 1 A subsynchronous oscillation component of (a);is a first time domain voltageV 1 Phase angle of medium fundamental frequency component, +.>Is a first time domain voltageV 1 Phase angle of the medium-sub-synchronous oscillation component, +.>Is the second time domain voltageV 2 Phase angle of medium fundamental frequency component, +.>Is the second time domain voltageV 2 Phase angle of the medium-sub-synchronous oscillation component, +.>Is a time domain currentI 1 Phase angle of medium fundamental frequency component, +.>Is a time domain currentI 1 Is provided, the phase angle of the subsynchronous oscillation component of (c),f 0 is the fundamental frequency of the frequency,f ω is the frequency of subsynchronous oscillations, +.>For the damping ratio of the subsynchronous oscillations,tis time.
And 2, calculating the voltage difference between two ends of the transmission line according to the time domain voltage between two ends of the transmission line measured in the step 1, and constructing an expression of the voltage difference between two ends of the transmission line according to the series compensation system and the time domain current on the transmission line.
In step 2, the voltage difference between two ends of the transmission line；
The series compensation system comprises a capacitor, an inductor and a resistor which are connected in series between two ends of a transmission line, and the expression of the voltage difference between the two ends of the constructed transmission line is as follows:
wherein ,Rrepresenting the resistance value of the resistor,Lrepresenting the inductance value of the inductor,Crepresenting the capacitance value of the capacitor in question,in the form of differentiation of the time-domain current, +.>In the form of an integral of the time-domain current, +.>Impedance angle of fundamental frequency component of voltage difference at two ends of transmission line, < >>Impedance angle of subsynchronous oscillation component for voltage difference between two ends of transmission line;
、/>the expression of (2) is:
。
as can be seen from the above formula, the voltage difference across the transmission lineIs composed of fundamental frequency component and SSR component.
And 3, obtaining the current time shift and the impedance by measuring, and calculating the auxiliary voltage drop according to the current time shift and the impedance.
Wherein the auxiliary voltage dropThe calculation formula of (2) is as follows:
wherein ,z is the current magnitude after time shift 0 Impedance which is the fundamental frequency component;
impedance Z of fundamental frequency component 0 The following strips are satisfiedPiece type:
。
and 4, obtaining a voltage waveform only comprising the subsynchronous oscillation component according to the voltage difference between two ends of the transmission line and the auxiliary voltage drop.
To eliminate the fundamental frequency component of the transmission line, a voltage waveform containing only the subsynchronous oscillation component is obtained based on the voltage difference between the two ends of the transmission line and the auxiliary voltage drop。
Wherein the voltage waveformThe expression of (2) is:
wherein ,Ain order to synchronize the amplitude of the oscillation,impedance for subsynchronous oscillation component, +.>Is the phase angle of the voltage;
、/>the following conditional expression is satisfied:
。
and step 5, extracting the frequency, damping ratio and amplitude of the subsynchronous oscillation according to the voltage waveform obtained in the step 4, and realizing the identification of the subsynchronous oscillation.
Wherein the voltage waveform obtained according to step 4By detecting->To obtain the frequency of subsynchronous oscillations at the moment of one zero crossing and at the moment of the subsequent peakf ω ，f ω The expression of (2) is:
wherein ,t 2 is the peak moment of the zero crossing of the voltage,t 1 is the moment when the voltage crosses the zero crossing point;
in step 5, the expression of the amplitude of the synchronous oscillation is:
in step 5, the damping ratio of the subsynchronous oscillation is calculated by the following formula:
wherein ,representing the time between the peaks of the two waveforms, +.>The current magnitude of the second peak current, +.>For the current magnitude of the first peak current, ln represents the logarithmic operator.
Furthermore, the method comprises the following steps:
when the subsynchronous oscillation is identified, calculating the actual synchronous oscillation component of the current waveform according to the frequency, the damping ratio and the amplitude of the synchronous oscillation obtained in the step 5，/>The expression of (2) is:
wherein ,representing the time offset.
It should be noted that the number of the components,is a current value, in the auxiliary voltage drop expression and the expression of current waveform, the time offset is +.>The current waveform of the SSR is negligible in practice, and for an integer number of samples, the shift of the integer samples is used to obtain the time shift closest to the auxiliary voltage drop and the desired value used for the current waveform.
The method of the invention was tested in a circuit consisting of a DFIG-based wind farm connected to the grid via a 200 km series compensation line. The method is designed in MATLAB/Simulink electric power system software, an induction motor adopts a six-fold model, and a generator shaft adopts a double-mass drive train model to control a rotor-side converter (RSC) and a grid-side converter (GSC).
Specifically, RSCs control active and reactive power injection of the generator, while GSCs control dc link voltage. A filter is added at the GSC inlet to eliminate switching frequency distortion, and a parallel RC branch is also added on the DFIG terminal to achieve the same purpose. These filters are suitable for high frequencies (in the order of kHz). The nominal frequency of the system is 60 Hz, the waveform sampling rate is 7680 Hz (128 samples/period), the wind speed is 10 m/s, and simulation results show that when the series compensation level of the line is increased from 30% to 50% of the line inductance, an SSR event is started at t=1s, so that the subsynchronous oscillation can be rapidly and accurately identified at an early stage by the method. Furthermore, according to the method, if the SSR current amplitude is small, the SSR frequency is determined and the SSR event is eliminated by taking measures, and if the SSR current amplitude is small, the SSR frequency is determined and the SSR event is positive damped, no measures are taken.
In summary, according to the method for identifying subsynchronous oscillation based on the measured waveform provided by the invention, an expression of a voltage difference at two ends of a transmission line is constructed according to a series compensation system and a time domain current on the transmission line, then the current time shift and impedance are obtained through measurement, and an auxiliary voltage drop is calculated according to the current time shift and impedance, so that a voltage waveform only containing a subsynchronous oscillation component is obtained, and finally the frequency, damping ratio and amplitude of the subsynchronous oscillation are extracted through the obtained voltage waveform, so that the subsynchronous oscillation is identified.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.

Claims (7)

1. A method for identifying subsynchronous oscillations based on a measured waveform, comprising:
step 1, measuring time domain voltages at two ends of a transmission line and time domain currents on the transmission line;
step 2, calculating the voltage difference between two ends of the transmission line according to the time domain voltages between two ends of the transmission line obtained by measuring in the step 1, and constructing an expression of the voltage difference between two ends of the transmission line according to the series compensation system and the time domain current on the transmission line;
step 3, obtaining the current time shift and impedance by measuring, and calculating auxiliary voltage drop according to the current time shift and the impedance;
step 4, obtaining a voltage waveform only comprising a subsynchronous oscillation component according to the voltage difference between two ends of the transmission line and the auxiliary voltage drop;
and step 5, extracting the frequency, damping ratio and amplitude of the subsynchronous oscillation according to the voltage waveform obtained in the step 4, and realizing the identification of the subsynchronous oscillation.
2. The method of claim 1, wherein in step 1, the time domain voltages across the transmission line are respectively the first time domain voltagesV 1 And a second time domain voltageV 2 Two transmission linesThe time domain voltage at the terminal and the time domain current on the transmission line satisfy the following conditional expression:
wherein ,V 10 is a first time domain voltageV 1 Is used for the matching of the fundamental frequency component of (c),V 1ω is a first time domain voltageV 1 Is used to determine the sub-synchronous oscillation component of the (c),V 20 is the second time domain voltageV 2 Is used for the matching of the fundamental frequency component of (c),V 2ω is the second time domain voltageV 2 Is used to determine the sub-synchronous oscillation component of the (c),I 10 is a time domain currentI 1 Is used for the matching of the fundamental frequency component of (c),I 1ω is a time domain currentI 1 A subsynchronous oscillation component of (a);is a first time domain voltageV 1 Phase angle of medium fundamental frequency component, +.>Is a first time domain voltageV 1 Phase angle of the medium-sub-synchronous oscillation component, +.>Is the second time domain voltageV 2 Phase angle of medium fundamental frequency component, +.>Is the second time domain voltageV 2 Phase angle of the medium-sub-synchronous oscillation component, +.>Is a time domain currentI 1 Phase angle of medium fundamental frequency component, +.>Is a time domain currentI 1 Phase angle of subsynchronous oscillation component of (2)，f 0 Is the fundamental frequency of the frequency,f ω is the frequency of subsynchronous oscillations, +.>For the damping ratio of the subsynchronous oscillations,tis time.
3. The method of claim 2, wherein in step 2, the voltage difference across the transmission line is determined by comparing the measured waveform with the reference voltage；
The series compensation system comprises a capacitor, an inductor and a resistor which are connected in series between two ends of a transmission line, and the expression of the voltage difference between the two ends of the constructed transmission line is as follows:
wherein ,Rrepresenting the resistance value of the resistor,Lrepresenting the inductance value of the inductor,Crepresenting the capacitance value of the capacitor in question,in the form of differentiation of the time-domain current, +.>In the form of an integral of the time-domain current, +.>Impedance angle of fundamental frequency component of voltage difference at two ends of transmission line, < >>Impedance angle of subsynchronous oscillation component for voltage difference between two ends of transmission line;
、/>the expression of (2) is:
。
4. the method of claim 3, wherein in step 3, the auxiliary voltage drop is determinedThe calculation formula of (2) is as follows:
wherein ,z is the current magnitude after time shift 0 Impedance which is the fundamental frequency component;
impedance Z of fundamental frequency component 0 The following conditional expression is satisfied:
。
5. the method of measuring waveform based subsynchronous oscillation identification of claim 4, wherein in step 4, the voltage waveform is generatedThe expression of (2) is:
wherein ,Ain order to synchronize the amplitude of the oscillation,impedance for subsynchronous oscillation component, +.>Is the phase angle of the voltage;
、/>the following conditional expression is satisfied:
。
6. the method for measuring waveform-based subsynchronous oscillation identification of claim 5, wherein in step 5, the voltage waveform obtained in step 4 is usedBy detecting->To obtain the frequency of subsynchronous oscillations at the moment of one zero crossing and at the moment of the subsequent peakf ω ，f ω The expression of (2) is:
wherein ,t 2 is the peak moment of the zero crossing of the voltage,t 1 is the moment when the voltage crosses the zero crossing point;
in step 5, the expression of the amplitude of the synchronous oscillation is:
in step 5, the damping ratio of the subsynchronous oscillation is calculated by the following formula:
wherein ,representing the time between the peaks of the two waveforms, +.>The current magnitude for the second peak current,for the current magnitude of the first peak current, ln represents the logarithmic operator.
7. The method of measuring waveform based subsynchronous oscillation identification of claim 6, further comprising:
when the subsynchronous oscillation is identified, calculating the actual synchronous oscillation component of the current waveform according to the frequency, the damping ratio and the amplitude of the synchronous oscillation obtained in the step 5，/>The expression of (2) is:
wherein ,representing the time offset.
CN202310920713.9A 2023-07-26 2023-07-26 Subsynchronous oscillation identification method based on measurement waveform Active CN116626433B (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016034249A1 (en) * 2014-09-05 2016-03-10 Abb Technology Ltd Monitoring torsional oscillations in a turbine-generator
CA3105143A1 (en) * 2018-07-06 2020-01-09 Wobben Properties Gmbh Method for controlling a wind farm in order to damp subsynchronous oscillations
CN110927449A (en) * 2019-11-28 2020-03-27 润电能源科学技术有限公司 Injection type subsynchronous oscillation frequency online monitoring method and system and power system
CN111525611A (en) * 2020-04-26 2020-08-11 西安热工研究院有限公司 Frequency coupling effect-considering doubly-fed grid-connected system subsynchronous oscillation analysis method
CN113346513A (en) * 2021-03-09 2021-09-03 江苏大学 Method for identifying forced subsynchronous oscillation of direct-drive fan
CN115833089A (en) * 2022-09-30 2023-03-21 国网陕西省电力有限公司电力科学研究院 Wind power system subsynchronous oscillation risk assessment method based on series compensation resistor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2016034249A1 (en) * 2014-09-05 2016-03-10 Abb Technology Ltd Monitoring torsional oscillations in a turbine-generator
CA3105143A1 (en) * 2018-07-06 2020-01-09 Wobben Properties Gmbh Method for controlling a wind farm in order to damp subsynchronous oscillations
CN110927449A (en) * 2019-11-28 2020-03-27 润电能源科学技术有限公司 Injection type subsynchronous oscillation frequency online monitoring method and system and power system
CN111525611A (en) * 2020-04-26 2020-08-11 西安热工研究院有限公司 Frequency coupling effect-considering doubly-fed grid-connected system subsynchronous oscillation analysis method
CN113346513A (en) * 2021-03-09 2021-09-03 江苏大学 Method for identifying forced subsynchronous oscillation of direct-drive fan
CN115833089A (en) * 2022-09-30 2023-03-21 国网陕西省电力有限公司电力科学研究院 Wind power system subsynchronous oscillation risk assessment method based on series compensation resistor

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