A multi-frequency coupling classification method and system for doubly-fed wind turbines under synchronous disturbances

Abstract

The application provides a synchronous disturbance double-fed wind turbine multi-frequency coupling classification method, comprising: applying different frequencies to the control response of a wind turbine converter to obtain components of three-phase voltage and current coupling generated frequencies of the double-fed wind turbine under different frequencies; obtaining a coupling rule of the double-fed wind turbine based on the components of three-phase voltage and current coupling generated frequencies of the double-fed wind turbine under different frequencies; and determining the frequencies of three-phase voltage and current of the double-fed wind turbine through the components of the to-be-acquired frequencies and the coupling rule. The application effectively classifies the multi-frequency coupling of the double-fed wind turbine under subsynchronous disturbance by combining the flux linkage coupling of the asynchronous motor of the double-fed wind turbine and the control response of the wind turbine converter.

Description

Technical Field

[0001] The present invention relates to a doubly-fed wind turbine generator set, and in particular to a multi-frequency coupling classification method and system for a doubly-fed wind turbine generator set under synchronous disturbance. Background Art

[0002] The frequency coupling characteristics of subsynchronous oscillations generally refer to the frequency of the system being f er After the subsynchronous oscillation, the voltage and current will also couple out supersynchronous frequency components (2f1-f er ), the output power is coupled out of the sub-synchronous power frequency complementary frequency component (f1-f er The existing technology cannot determine the relationship between the frequency distribution of these coupled sub / supersynchronous components and the subsynchronous oscillation frequency of the system, and use the supersynchronous disturbance component under subsynchronization. Summary of the Invention

[0003] In view of the fact that the existing technology cannot classify the multi-frequency coupling of doubly-fed wind turbines under synchronous disturbance, the present invention provides a multi-frequency coupling classification method for doubly-fed wind turbines under synchronous disturbance, comprising:

[0004] Apply different frequencies to the control response of the wind turbine converter to obtain the frequency components generated by the three-phase voltage and current coupling of the doubly fed wind turbine at different frequencies;

[0005] The coupling law of the doubly-fed wind turbine is obtained based on the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine at different frequencies;

[0006] The frequencies of the three-phase voltage and current of the doubly-fed wind turbine generator system are determined by the components of the frequency to be obtained and the coupling law.

[0007] Preferably, the control response of the wind turbine converter is applied with different frequencies to obtain the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine generator set at different frequencies, including:

[0008] Based on the current inner loop control response characteristics of the rotor-side converter and the grid-side converter at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine are obtained;

[0009] Based on the phase-locked loop control response characteristics at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly fed wind turbine are obtained.

[0010] Preferably, the obtaining of the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine generator set based on the current inner loop control response characteristics of the rotor-side converter and the grid-side converter at different frequencies includes:

[0011] Calculate the rotor voltage disturbance component based on the corresponding voltage disturbance component generated in the rotor voltage command value output by the rotor-side converter and the current disturbance components and voltage disturbance amplitude and phase of the rotor d-axis and q-axis;

[0012] The rotor voltage disturbance component is converted into a three-phase stationary coordinate system, and a single-phase disturbance voltage component of a rotor side voltage command value is calculated according to the amplitude and phase of the rotor voltage disturbance component in the three-phase stationary coordinate system;

[0013] When the frequency is ω er When the three-phase disturbance current is , the grid-side converter voltage disturbance component is calculated based on the d-axis and q-axis disturbance components of the grid-side converter output voltage command value and the amplitude and phase of the voltage disturbance;

[0014] The grid-side converter voltage disturbance component is converted to a three-phase stationary coordinate system, and the stator side three-phase voltage disturbance voltage is calculated based on the amplitude and phase of the stator voltage disturbance component in the three-phase stationary coordinate system.

[0015] Preferably, the obtaining of the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine generator system based on the phase-locked loop control response characteristics at different frequencies includes:

[0016] Based on the grid voltage in the rotor d-axis and q-axis coordinate systems, determine the time domain expression of the phase-locked loop output phase angle disturbance;

[0017] Determining the rotor current in the d-axis and q-axis coordinate systems based on the time domain expression of the output disturbance of the phase-locked loop;

[0018] Based on the rotor current and phase-locked loop control response characteristics in the d-axis and q-axis coordinate systems, a frequency component generated by stator voltage coupling in the d-axis and q-axis coordinate systems is obtained.

[0019] Preferably, obtaining the frequency component generated by the stator voltage coupling in the d-axis and q-axis coordinate systems based on the rotor current and phase-locked loop control response characteristics in the d-axis and q-axis coordinate systems includes:

[0020] When the frequency of the output phase angle disturbance of the phase-locked loop is (ω1-ω er ) is disturbed, the stator voltage in the d-axis and q-axis coordinate systems is coupled based on the output phase angle disturbance of the phase-locked loop and the rotor current in the d-axis and q-axis coordinate systems to obtain a frequency of 2(ω1-ω er )

[0021] When the frequency of the output phase angle disturbance of the phase-locked loop is 2(ω1-ω er ) component, based on the grid voltage and the output phase angle disturbance of the phase-locked loop, the grid voltage is coupled to obtain a frequency of n(ω1-ω er )'s frequency multiple.

[0022] Preferably, the method of obtaining the coupling law of the doubly-fed wind turbine generator system based on the frequency components generated by coupling of the three-phase voltage and current of the doubly-fed wind turbine generator system at different frequencies includes:

[0023] When the frequency generated in the stator voltage and current in the three-phase stationary coordinate system is ω er When the disturbance is generated, the stator and rotor voltage and current generation frequency in the synchronous rotating coordinate system is (ω1-ω er )’s disturbance component;

[0024] When the frequency in the wind turbine converter is (ω1-ω er ) disturbance, the frequency generated by the coupling in the three-phase stator voltage and current of the doubly fed wind turbine is ω er The subsynchronous component and frequency are (2ω1-ω er )'s supersynchronous component;

[0025] When the phase-locked loop is subjected to subsynchronous disturbance, the coupling frequency in the voltage and current of the doubly fed wind turbine in the synchronous rotating coordinate system is n(ω1-ω er )’s frequency multiplication component;

[0026] When the coupling in the phase-locked loop generates n(ω1-ω er ) frequency components, the frequency generated by coupling in the three-phase stator voltage and current of the doubly fed wind turbine is n(ω1-ω er )±ω1 components.

[0027] Preferably, the corresponding voltage disturbance component generated in the rotor voltage command value output by the rotor-side converter is calculated as follows:

[0028]

[0029] Where: Δi dr is the rotor d-axis current disturbance component; Δi qr is the rotor q-axis current disturbance component; K p2 K is the RSC current inner loop proportional coefficient; i2 is the RSC current inner loop integral coefficient; Δu dr is the rotor d-axis voltage command disturbance component; Δu qr is the disturbance component of the rotor q-axis voltage command.

[0030] The rotor voltage disturbance component is calculated as follows:

[0031]

[0032] Where: ω1 is the synchronous speed; ω er is the three-phase voltage frequency; t is the time; U er is the subsynchronous disturbance voltage amplitude; d-axis phase of the voltage disturbance; The q-axis phase of the voltage disturbance.

[0033] Preferably, the single-phase disturbance voltage component of the rotor side voltage command value is calculated as follows:

[0034]

[0035] Where Δu ar is the single-phase disturbance voltage component of the rotor side voltage command value; ω r is the frequency; U r1 is the frequency (2f1-f r -f er )’s voltage disturbance component amplitude; is the frequency (2f1-f r -f er ) of the voltage disturbance component phase; U r2 is the frequency (f r -f er )’s voltage disturbance component amplitude; is the frequency (f r -f er )’s voltage disturbance component phase.

[0036] Preferably, the grid-side converter voltage disturbance component is calculated as follows:

[0037]

[0038] Where U g is the amplitude of the disturbance component of the output voltage command value on the GSC side; Δu dg is the d-axis disturbance component of the output voltage command value on the GSC side; Δu qg is the q-axis disturbance component of the output voltage command value on the GSC side; is the phase of the d-axis disturbance component of the output voltage command value on the GSC side; is the phase of the q-axis disturbance component of the output voltage command value on the GSC side;

[0039] The disturbance voltage of the three-phase voltage on the stator side is calculated as follows:

[0040]

[0041] Where Δu as is the disturbance voltage of the three-phase voltage on the stator side; U s1 is the frequency (2f1-f er ) of the stator side voltage disturbance component; is the frequency (2f1-f er ) of the stator side voltage disturbance component phase; U s2is the frequency f er The amplitude of the stator side voltage disturbance component; is the frequency f er The phase of the stator side voltage disturbance component.

[0042] Preferably, the time domain expression of the output phase angle disturbance of the phase-locked loop is as shown below:

[0043]

[0044] Where Δθ is the time domain expression of the output phase angle disturbance of the phase-locked loop; u qs is the stator side voltage; K pp is the phase-locked loop proportional coefficient; K pi is the phase-locked loop integral coefficient;

[0045] The rotor current in the d-axis and q-axis coordinate systems is shown in the following formula:

[0046]

[0047] Where: A dr0 is the DC component of the rotor d-axis current; A dr1 is the frequency (f1-f er ) of the rotor d-axis current disturbance component; A dr2 is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component; A qr0 is the DC component of the rotor q-axis current; A qr1 is the frequency (f1-f er ) of the rotor q-axis current disturbance component; A qr2 is the frequency 2(f1-f er ) of the rotor q-axis current disturbance component; is the frequency (f1-f er ) of the rotor d-axis current disturbance component phase; is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component phase; is the frequency (f1-f er ) of the rotor d-axis current disturbance component phase; is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component.

[0048] Based on the same inventive concept, the present invention also provides a multi-frequency coupling classification system for doubly-fed wind turbines under synchronous disturbances, comprising: an acquisition module, a rule module, and a determination module;

[0049] The acquisition module applies different frequencies to the control response of the wind turbine converter to obtain the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine at different frequencies;

[0050] The law module is used to obtain the coupling law of the doubly-fed wind turbine generator system based on the components of the frequency generated by the coupling of the three-phase voltage and current of the doubly-fed wind turbine generator system at different frequencies;

[0051] The determination module determines the frequencies of the three-phase voltage and current of the doubly-fed wind turbine generator set according to the components of the frequencies to be acquired and the coupling law.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The present invention provides a method for classifying multi-frequency coupling of doubly-fed wind turbines under synchronous disturbances, comprising: applying different frequencies to the control response of a wind turbine converter to obtain the components of the frequencies generated by the coupling of the three-phase voltage and current of the doubly-fed wind turbine at different frequencies; obtaining the coupling law of the doubly-fed wind turbine based on the components of the frequencies generated by the coupling of the three-phase voltage and current of the doubly-fed wind turbine at different frequencies; determining the frequencies of the three-phase voltage and current of the doubly-fed wind turbine through the components of the frequencies to be obtained and the coupling law; the present invention effectively classifies the multi-frequency coupling of the doubly-fed wind turbines under subsynchronous disturbances by combining the flux coupling effect of the asynchronous motor of the doubly-fed wind turbine with the control response of the wind turbine converter.

[0054] 2. By analyzing the doubly fed wind turbines under various synchronous disturbances, the flux coupling effect of the asynchronous motor and the control response of the wind turbine controller are combined, and the results are used to classify the frequency coupling of the doubly fed wind turbines under subsynchronous disturbances. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The figure is a flow chart of the multi-frequency coupling classification analysis method of the doubly-fed wind turbine generator system under synchronous disturbance of the present invention. DETAILED DESCRIPTION

[0056] The embodiments of the present invention will be further described with reference to the accompanying drawings.

[0057] Example 1

[0058] Combine Figure 1 The present invention provides a multi-frequency coupling classification method for doubly-fed wind turbines under synchronous disturbance, comprising:

[0059] Step 1: Apply different frequencies to the control response of the wind turbine converter to obtain the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine at different frequencies;

[0060] Step 2: Obtain the coupling law of the doubly-fed wind turbine generator system based on the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine generator system at different frequencies;

[0061] Step 3: Determine the frequencies of the three-phase voltage and current of the doubly-fed wind turbine generator system through the components of the frequency to be obtained and the coupling law.

[0062] Among them, step 1: applying different frequencies to the control response of the wind turbine converter to obtain the components of the frequency generated by the three-phase voltage and current coupling of the doubly fed wind turbine at different frequencies, including:

[0063] Based on the current inner loop control response characteristics of the rotor-side converter and the grid-side converter at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine are obtained;

[0064] Based on the phase-locked loop control response characteristics at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly fed wind turbine are obtained.

[0065] Based on the current inner loop control response characteristics of the rotor-side converter and the grid-side converter at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine are obtained, including:

[0066] Calculate the rotor voltage disturbance component based on the corresponding voltage disturbance component generated in the rotor voltage command value output by the rotor-side converter and the current disturbance components and voltage disturbance amplitude and phase of the rotor d-axis and q-axis;

[0067] The rotor voltage disturbance component is converted into a three-phase stationary coordinate system, and the single-phase disturbance voltage component of the rotor side voltage command value is calculated according to the amplitude and phase of the rotor voltage disturbance component in the three-phase stationary coordinate system;

[0068] When the frequency is ω er When the three-phase disturbance current is , the grid-side converter voltage disturbance component is calculated based on the d-axis and q-axis disturbance components of the grid-side converter output voltage command value and the amplitude and phase of the voltage disturbance;

[0069] The grid-side converter voltage disturbance component is converted to a three-phase stationary coordinate system, and the stator side three-phase voltage disturbance voltage is calculated based on the amplitude and phase of the stator voltage disturbance component in the three-phase stationary coordinate system.

[0070] Based on the phase-locked loop control response characteristics at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly fed wind turbine are obtained, including:

[0071] Based on the grid voltage in the rotor d-axis and q-axis coordinate systems, determine the time domain expression of the phase-locked loop output phase angle disturbance;

[0072] Based on the time domain expression of the output disturbance of the phase-locked loop, the rotor current in the d-axis and q-axis coordinate systems is determined;

[0073] Based on the rotor current and phase-locked loop control response characteristics in the d-axis and q-axis coordinate systems, the frequency components generated by the stator voltage coupling in the d-axis and q-axis coordinate systems are obtained.

[0074] Based on the rotor current and phase-locked loop control response characteristics in the d-axis and q-axis coordinate systems, the frequency components generated by the stator voltage coupling in the d-axis and q-axis coordinate systems are obtained, including:

[0075] When the frequency of the output phase angle disturbance of the phase-locked loop is (ω1-ω er ) is disturbed, the stator voltage in the d-axis and q-axis coordinate systems is coupled based on the output phase angle disturbance of the phase-locked loop and the rotor current in the d-axis and q-axis coordinate systems to obtain a frequency of 2(ω1-ω er )

[0076] When the frequency of the output phase angle disturbance of the phase-locked loop is 2(ω1-ω er ) component, based on the grid voltage and the output phase angle disturbance of the phase-locked loop, the grid voltage is coupled to obtain a frequency of n(ω1-ω er )'s frequency multiple.

[0077] Among them, step 2: obtaining the coupling law of the doubly fed wind turbine generator system based on the components of the frequency generated by the three-phase voltage and current coupling of the doubly fed wind turbine generator system at different frequencies, including:

[0078] When the frequency generated in the stator voltage and current in the three-phase stationary coordinate system is ω er When the disturbance is generated, the stator and rotor voltage and current generation frequency in the synchronous rotating coordinate system is (ω1-ω er )’s disturbance component;

[0079] When the frequency in the wind turbine converter is (ω1-ω er ) disturbance, the frequency generated by the coupling in the three-phase stator voltage and current of the doubly fed wind turbine is ω er The subsynchronous component and frequency are (2ω1-ω er )'s supersynchronous component;

[0080] When the phase-locked loop is subjected to subsynchronous disturbance, the coupling frequency in the voltage and current of the doubly fed wind turbine in the synchronous rotating coordinate system is n(ω1-ω er )’s frequency multiplication component;

[0081] When the coupling in the phase-locked loop generates n(ω1-ω er ) frequency components, the frequency generated by coupling in the three-phase stator voltage and current of the doubly fed wind turbine is n(ω1-ω er )±ω1 components.

[0082] The corresponding voltage disturbance component generated in the rotor voltage command value output by the rotor-side converter is calculated as follows:

[0083]

[0084] Where: Δi dr is the rotor d-axis current disturbance component; Δi qr is the rotor q-axis current disturbance component; K p2 K is the RSC current inner loop proportional coefficient; i2 is the RSC current inner loop integral coefficient; Δu dr is the rotor d-axis voltage command disturbance component; Δu qr is the disturbance component of the rotor q-axis voltage command.

[0085] The rotor voltage disturbance component is calculated as follows:

[0086]

[0087] Where: ω1 is the synchronous speed; ω er is the three-phase voltage frequency; t is the time; U er is the subsynchronous disturbance voltage amplitude; d-axis phase of the voltage disturbance; The q-axis phase of the voltage disturbance.

[0088] The single-phase disturbance voltage component of the rotor side voltage command value is calculated as follows:

[0089]

[0090] Where Δu ar is the single-phase disturbance voltage component of the rotor side voltage command value; ω r is the frequency; U r1 is the frequency (2f1-f r -f er )’s voltage disturbance component amplitude; is the frequency (2f1-f r -f er ) of the voltage disturbance component phase; U r2 is the frequency (f r -f er )’s voltage disturbance component amplitude; is the frequency (f r -f er )’s voltage disturbance component phase.

[0091] The voltage disturbance component of the grid-side converter is calculated as follows:

[0092]

[0093] Where U g is the amplitude of the disturbance component of the output voltage command value on the GSC side; Δu dg is the d-axis disturbance component of the output voltage command value on the GSC side; Δu qg is the q-axis disturbance component of the output voltage command value on the GSC side; is the phase of the d-axis disturbance component of the output voltage command value on the GSC side; is the phase of the q-axis disturbance component of the output voltage command value on the GSC side;

[0094] The disturbance voltage of the three-phase voltage on the stator side is calculated as follows:

[0095]

[0096] Where Δu as is the disturbance voltage of the three-phase voltage on the stator side; U s1 is the frequency (2f1-f er ) of the stator side voltage disturbance component; is the frequency (2f1-f er ) of the stator side voltage disturbance component phase; U s2 is the frequency f er The amplitude of the stator side voltage disturbance component; is the frequency f er The phase of the stator side voltage disturbance component.

[0097] The time domain expression of the output phase angle disturbance of the phase-locked loop is shown as follows:

[0098]

[0099] Where Δθ is the time domain expression of the output phase angle disturbance of the phase-locked loop; u qs is the stator side voltage; K pp is the phase-locked loop proportional coefficient; K pi is the phase-locked loop integral coefficient;

[0100] The rotor current in the d-axis and q-axis coordinate systems is shown in the following equation:

[0101]

[0102] Where: A dr0 is the DC component of the rotor d-axis current; A dr1 is the frequency (f1-f er ) of the rotor d-axis current disturbance component; A dr2 is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component; A qr0 is the DC component of the rotor q-axis current; Aqr1 is the amplitude of the disturbance component of the rotor q-axis current at the frequency (f1 - f er ); A qr2 is the amplitude of the disturbance component of the rotor q-axis current at the frequency 2(f1 - f er ); is the phase of the disturbance component of the rotor d-axis current at the frequency (f1 - f er ); is the phase of the disturbance component of the rotor d-axis current at the frequency 2(f1 - f er ); is the phase of the disturbance component of the rotor d-axis current at the frequency (f1 - f er ); is the phase of the disturbance component of the rotor d-axis current at the frequency 2(f1 - f er ).

[0103] Embodiment 2

[0104] A multi-frequency coupling classification method for a doubly-fed wind turbine under synchronous disturbance proposed by the present invention includes the following steps:

[0105] I. Analyze from the flux linkage coupling effect of the asynchronous motor;

[0106] II. Analyze from the control response of the wind turbine converter;

[0107] III. Sort out the frequency coupling law and conduct frequency coupling classification.

[0108] Further, in step I, analyze from the flux linkage coupling effect of the asynchronous motor.

[0109] When the doubly-fed wind turbine operates in a steady state, since the rotor speed frequency is f r , the frequency of the rotor three-phase current is the slip frequency (f1 - f r ). When the DFIG operates supersynchronously (f r > f1), it means that the rotational speed of the rotating magnetic field generated by the rotor current is opposite to the rotor speed direction; when sub-synchronously operating (f r < f1), the rotational speed of the rotating magnetic field generated by the rotor current is the same as the rotor speed direction. And when a sub-synchronous disturbance current with a frequency of f er appears in the power grid, through the flux linkage coupling effect between the DFIG stator and rotor, a disturbance component with a frequency of (f er - f r ) will be coupled in the rotor three-phase current, that is:

[0110]

[0111] Where: I er is the current disturbance amplitude, Δi ar is the frequency (fer -f r ) of the a-phase current disturbance component, Δi br is the frequency (f er -f r ) of the b-phase current disturbance component, Δi cr is the frequency (f er -f r ) of the c-phase current disturbance component.

[0112] Convert the rotor three-phase current disturbance to the synchronous rotating coordinate system, and the frequency of the rotor d and q axis current disturbance is (f1-f er ):

[0113]

[0114] ω1 is the synchronous speed, Δi dr is the rotor d-axis current disturbance component, Δi qr is the rotor q-axis current disturbance component, and the matrix T is:

[0115]

[0116] Where θ P ' LL is the phase-locked phase.

[0117] When the frequency of the three-phase voltage of the power grid is ω er When a subsynchronous disturbance occurs, if it is assumed that the disturbance is three-phase symmetrical and the initial phase is zero, the three-phase voltage of the power grid is:

[0118]

[0119] Where: U1 is the power frequency voltage amplitude, U er is the subsynchronous disturbance voltage amplitude, u as Grid phase a voltage, u bs Grid phase b voltage, u cs Grid phase C voltage.

[0120] By transforming the three-phase stationary coordinate system into the synchronous rotating coordinate system, the grid voltage in the dq coordinate system can be obtained as:

[0121]

[0122] Where: u ds Grid d-axis voltage, u qs Grid q-axis voltage.

[0123] In the grid voltage in the dq coordinate system, in addition to the steady-state DC component, a frequency of (ω1-ω er) disturbance component, the frequency distribution characteristics of the rotor voltage and current in the dq coordinate system are the same as those of the stator, and will also include these two frequency components.

[0124] Furthermore, in step II, analysis is performed based on the control response of the wind turbine converter.

[0125] RSC and GSC current inner loop control response characteristics

[0126] Assuming that the rotor current reference value remains unchanged, the rotor current disturbance will cause a corresponding voltage disturbance in the RSC output rotor voltage command value after being controlled by the RSC current inner loop:

[0127]

[0128] Where: K p2 K is the RSC current inner loop proportional coefficient, i2 is the RSC current inner loop integral coefficient, Δu dr is the rotor d-axis voltage command disturbance component, Δu qr is the disturbance component of the rotor q-axis voltage command.

[0129] The rotor voltage disturbance is calculated as:

[0130]

[0131] Where: The d-axis phase of the voltage disturbance, The q-axis phase of the voltage disturbance.

[0132] The specific expressions of the amplitude and phase of the voltage disturbance are:

[0133]

[0134] The rotor voltage disturbance is converted to the three-phase stationary coordinate system, and the rotor voltage command value a-phase disturbance voltage is obtained as:

[0135]

[0136] U r1 is the frequency (2f1-f r -f er )’s voltage disturbance component amplitude, is the frequency (2f1-f r -f er ) voltage disturbance component phase, U r2 is the frequency (f r -f er )’s voltage disturbance component amplitude, is the frequency (f r -f erThe specific expressions of the voltage disturbance component phase of the rotor voltage disturbance are as follows:

[0137]

[0138] The frequency in the power grid is f er After the subsynchronous disturbance is controlled by RSC, the rotor voltage is coupled with a frequency of (f r -f er ) and (2f1-f r -f er The change in rotor voltage, through the magnetic coupling between the stator and rotor, will induce new subsynchronous disturbances in the stator voltage and current.

[0139] Calculations show that when a subsynchronous frequency disturbance component exists in the stator current, the control system of a doubly-fed wind turbine generator system not only superimposes the corresponding frequency components in the stator and rotor voltages and currents, but also couples new frequency components, effectively increasing the negative damping of the entire system. This means that the "negative damping effect" of a doubly-fed wind turbine generator system under subsynchronous disturbances stems partly from the negative rotor equivalent resistance at the subsynchronous frequency and partly from the superposition of subsynchronous components caused by the turbine control system. Therefore, the subsynchronous oscillations caused by grid-connected doubly-fed wind turbines are closely related not only to the parameters of the electrical system but also to the control parameters of the power electronic converter.

[0140] Without considering the influence of subsynchronous disturbance on the phase angle of the phase-locked loop output, the response process of the RSC current inner loop to subsynchronous disturbance is: er Under the subsynchronous disturbance, after the control of RSC, the three-phase rotor voltage is coupled with a frequency (2ω1-ω r -ω er ) in the rotor. r -ω er ) component is coupled through the magnetic flux coupling between the stator and rotor, and the stator three-phase voltage and current will couple out a frequency of (2ω1-ω er ) of the supersynchronous component.

[0141] At the same time, at a frequency of ω er Under the three-phase disturbance current, the GSC side current in the synchronous rotating coordinate system will also contain a frequency of (ω1-ω er )’s disturbance component:

[0142]

[0143] Where: I g is the current disturbance amplitude on the GSC side, Δi dg is the d-axis component of the current disturbance on the GSC side, Δi qgis the q-axis component of the current disturbance on the GSC side.

[0144] The structure and control logic of the GSC current inner loop are similar to those of the RSC. After the disturbance current passes through the GSC current inner loop, a corresponding voltage disturbance will be generated in the output voltage command value on the GSC side:

[0145]

[0146] U g is the amplitude of the disturbance component of the output voltage command value on the GSC side, Δu dg is the d-axis disturbance component of the output voltage command value on the GSC side, is the phase of the d-axis disturbance component of the output voltage command value on the GSC side, is the phase of the q-axis disturbance component of the output voltage command value on the GSC side, and its amplitude and phase are:

[0147]

[0148] Where: K p4 K is the GSC current inner loop proportional coefficient, i4 is the GSC current inner loop integral coefficient.

[0149] The voltage disturbance on the GSC side is converted to the three-phase stationary coordinate system, and the disturbance voltage in the three-phase voltage on the stator side is:

[0150]

[0151] U s1 is the frequency (2f1-f er ), is the frequency (2f1-f er ) of the stator side voltage disturbance component phase, U s2 is the frequency f er The amplitude of the stator side voltage disturbance component, is the frequency f er The phase of the stator side voltage disturbance component, its amplitude and phase are:

[0152]

[0153] By calculating the response process of RSC and GSC to subsynchronous disturbance, it is found that when the output phase angle disturbance of the phase-locked loop is not considered, the frequency is (ω1-ω er ) acts on the wind turbine converter, which will cause the DFIG three-phase voltage and current to couple out a frequency of ω er and (2ω1-ω er )'s weight.

[0154] 2) Phase-locked loop control response characteristics

[0155] Further considering the impact of subsynchronous disturbances in the grid voltage on the phase angle of the phase-locked loop output, the time domain expression of the phase-locked loop output phase angle disturbance Δθ can be obtained as:

[0156]

[0157] Where K pp is the phase-locked loop proportional coefficient, K pi is the phase-locked loop integral coefficient.

[0158] Considering the influence of the output disturbance of the phase-locked loop on the rotor current, the rotor current in the dq coordinate system can be obtained as:

[0159]

[0160] A dr0 is the DC component of the rotor d-axis current, A dr1 is the frequency (f1-f er ) of the rotor d-axis current disturbance component, A dr2 is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component, A qr0 is the DC component of the rotor q-axis current, A qr1 is the frequency (f1-f er ) of the rotor q-axis current disturbance component, A qr2 is the frequency 2(f1-f er ) of the rotor q-axis current disturbance component, is the frequency (f1-f er ) of the rotor d-axis current disturbance component phase, is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component phase, is the frequency (f1-f er ) of the rotor d-axis current disturbance component phase, is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component phase, and its coefficients are:

[0161]

[0162] The subsynchronous disturbance in the system will cause the phase angle of the phase-locked loop to be disturbed by Δθ; the frequency in Δθ is (ω1-ω er ) makes the stator voltage in the dq coordinate system coupled with a frequency of 2(ω1-ω er ) of the new component. The frequency is 2(ω1-ω er) component, whose amplitude is related to factors such as subsynchronous disturbance amplitude, phase-locked loop control parameters, and subsynchronous oscillation angular frequency. It can be seen from the amplitude expression that: U in the numerator er The square value of is small, and the value of the angular frequency in the denominator is large, so the frequency is 2(ω1-ω er ) has a small amplitude. If we further consider that the new voltage and output phase angle disturbance continue to act on the phase-locked loop, after iteration, the grid voltage will eventually couple a frequency of n(ω1-ω er )(n=1,2,3,……)’s frequency harmonic components.

[0163] Since the input and output signals of RSC and GSC will use the output phase angle of PLL, the n(ω1-ω er ) after the double frequency disturbance component acts on the wind turbine converter, it will cause the DFIG three-phase voltage and current to couple out a frequency of n(ω1-ω er )±ω1 components.

[0164] Furthermore, in step III, the frequency coupling rules are sorted out and frequency coupling classification is carried out.

[0165] III. Sort out the frequency coupling rules and carry out frequency coupling classification.

[0166] Under subsynchronous disturbances, the multi-frequency coupling process of the doubly fed wind turbine can be summarized as follows:

[0167] 1) When the frequency of the stator voltage and current in the three-phase stationary coordinate system is ω er When the stator voltage and current in the synchronous rotating coordinate system are disturbed by the frequency (ω1-ω er ) disturbance component; Due to the magnetic coupling between the stator and rotor windings, the rotor voltage and current in the synchronous rotating coordinate system will also contain (ω1-ω er ) frequency disturbance component.

[0168] 2) The frequency is (ω1-ω er ) acts on the wind turbine converter, which will cause the DFIG three-phase stator voltage and current to couple out a frequency of ω er The subsynchronous component and frequency are (2ω1-ω er ) of the supersynchronous component.

[0169] 3) Considering the influence of subsynchronous disturbance on the phase angle of the phase-locked loop output, the dynamic control of the phase-locked loop will make the frequency of the coupled DFIG voltage and current in the synchronous rotating coordinate system n(ω1-ω er )(n=1,2,3,……)’s frequency harmonic components.

[0170] 4) n(ω1-ω) coupled by the phase-locked looper ) frequency multiplier component, continues to act on the wind turbine converter, and the DFIG three-phase stator voltage and current will couple out a frequency of n(ω1-ω er )±ω1 components.

[0171] The multi-frequency coupling rules in DFIG voltage and current under subsynchronous disturbances can be summarized in Table 1. According to the rules in Table 1, the relevant subsynchronous disturbances are classified.

[0172] Since the fan controller has the characteristics of multi-scale control and the frequency-multiplied components coupled by the phase-locked loop participate in multiple control links, it is relatively complicated to quantitatively derive the specific expression of the amplitude of each frequency component. However, summarizing its general amplitude distribution law, it can be seen that in the synchronous rotating coordinate system, except for the steady-state DC component, (ω1-ω er ) frequency component has the largest amplitude because it is directly coupled to the subsynchronous disturbance component in the three-phase coordinate system. From the previously derived phase-locked loop response process, we know that 2(ω1-ω er ),3(ω1-ω er ) and other frequencies have a small amplitude; in the three-phase stationary coordinate system, in addition to the power frequency component, the subsynchronous frequency ω er The amplitude is the largest, which is determined by the synchronous rotating coordinate system (ω1-ω er )The frequency coupled by the frequency component is (2ω1-ω er ) has a larger supersynchronous component amplitude, and the other components have smaller amplitudes. Similarly, in the rotor electric quantity of the three-phase stationary coordinate system, except for (ω1-ω r ) frequency steady-state component, the frequency is (ω r -ω er ) and (2ω1-ω r -ω er ) has a larger component amplitude.

[0173] Table 1 Multi-frequency coupling law of doubly fed wind turbines under subsynchronous disturbance

[0174]

[0175]

[0176] Example 3

[0177] Based on the same inventive concept, the present invention also provides a multi-frequency coupling classification system for doubly-fed wind turbines under synchronous disturbances, comprising: an acquisition module, a rule module, and a determination module;

[0178] Acquisition module: Apply different frequencies to the control response of the wind turbine converter to obtain the frequency components generated by the three-phase voltage and current coupling of the doubly fed wind turbine at different frequencies;

[0179] Law module: obtains the coupling law of the doubly-fed wind turbine generator system based on the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine generator system at different frequencies;

[0180] Determination module: Determine the frequency of the three-phase voltage and current of the doubly fed wind turbine generator set through the components and coupling rules of the frequency to be obtained.

[0181] The acquisition module includes rotor-side converter and grid-side converter submodules and a phase-locked loop control response characteristic subsystem;

[0182] Rotor-side converter and grid-side converter submodules: Based on the current inner-loop control response characteristics of the rotor-side converter and grid-side converter at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine are obtained;

[0183] Phase-locked loop control response characteristic subsystem: Based on the phase-locked loop control response characteristics at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly fed wind turbine are obtained.

[0184] The phase-locked loop control response characteristic subsystem includes an expression unit, a rotor current unit and a frequency component unit;

[0185] Based on the grid voltage in the rotor d-axis and q-axis coordinate systems, determine the time domain expression of the phase-locked loop output phase angle disturbance;

[0186] Determining the rotor current in the d-axis and q-axis coordinate systems based on the time domain expression of the output disturbance of the phase-locked loop;

[0187] Based on the rotor current and phase-locked loop control response characteristics in the d-axis and q-axis coordinate systems, a frequency component generated by stator voltage coupling in the d-axis and q-axis coordinate systems is obtained.

[0188] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0189] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0190] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0191] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0192] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A multi-frequency coupling classification method for doubly-fed wind turbines under synchronous disturbances, characterized in that: include: Apply different frequencies to the control response of the wind turbine converter to obtain the frequency components generated by the three-phase voltage and current coupling of the doubly fed wind turbine at different frequencies; The coupling law of the doubly-fed wind turbine is obtained based on the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine at different frequencies; Determine the frequencies of the three-phase voltage and current of the doubly-fed wind turbine generator set through the components of the frequencies to be acquired and the coupling law; The method of obtaining the coupling law of the doubly-fed wind turbine generator system based on the frequency components generated by the coupling of the three-phase voltage and current of the doubly-fed wind turbine generator system at different frequencies includes: When the frequency generated in the stator voltage and current in the three-phase stationary coordinate system is ω er When the disturbance is generated, the stator and rotor voltage and current generation frequency in the synchronous rotating coordinate system is (ω1-ω er )’s disturbance component; When the frequency in the wind turbine converter is (ω1-ω er ) disturbance, the frequency generated by the coupling in the three-phase stator voltage and current of the doubly fed wind turbine is ω er The subsynchronous component and frequency are (2ω1-ω er )'s supersynchronous component; When the phase-locked loop is subjected to subsynchronous disturbance, the coupling frequency in the voltage and current of the doubly fed wind turbine in the synchronous rotating coordinate system is n(ω1-ω er )’s frequency multiplication component; When the coupling in the phase-locked loop generates n(ω1-ω er ) frequency components, the frequency generated by coupling in the three-phase stator voltage and current of the doubly fed wind turbine is n(ω1-ω er )±ω1 components.

2. The method according to claim 1, wherein The control response of the wind turbine converter is applied with different frequencies to obtain the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine generator set at different frequencies, including: Based on the current inner loop control response characteristics of the rotor-side converter and the grid-side converter at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine are obtained; Based on the phase-locked loop control response characteristics at different frequencies, the frequency components generated by the three-phase voltage and current coupling of the doubly fed wind turbine are obtained.

3. The method according to claim 2, characterized in that The method of obtaining the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine generator set based on the current inner loop control response characteristics of the rotor-side converter and the grid-side converter at different frequencies includes: Calculate the rotor voltage disturbance component based on the corresponding voltage disturbance component generated in the rotor voltage command value output by the rotor-side converter and the current disturbance components and voltage disturbance amplitude and phase of the rotor d-axis and q-axis; The rotor voltage disturbance component is converted into a three-phase stationary coordinate system, and a single-phase disturbance voltage component of a rotor side voltage command value is calculated according to the amplitude and phase of the rotor voltage disturbance component in the three-phase stationary coordinate system; When the frequency is ω er When the three-phase disturbance current is , the grid-side converter voltage disturbance component is calculated based on the d-axis and q-axis disturbance components of the grid-side converter output voltage command value and the amplitude and phase of the voltage disturbance; The grid-side converter voltage disturbance component is converted into a three-phase stationary coordinate system, and the stator side three-phase voltage disturbance voltage is calculated according to the amplitude and phase of the stator voltage disturbance component in the three-phase stationary coordinate system.

4. The method according to claim 3, characterized in that The frequency components generated by coupling of three-phase voltage and current of the doubly-fed wind turbine generator system are obtained based on the phase-locked loop control response characteristics at different frequencies, including: Based on the grid voltage in the rotor d-axis and q-axis coordinate systems, determine the time domain expression of the phase-locked loop output phase angle disturbance; Determining the rotor current in the d-axis and q-axis coordinate systems based on the time domain expression of the output disturbance of the phase-locked loop; Based on the rotor current and phase-locked loop control response characteristics in the d-axis and q-axis coordinate systems, a frequency component generated by stator voltage coupling in the d-axis and q-axis coordinate systems is obtained.

5. The method according to claim 4, wherein The obtaining of the frequency component generated by the stator voltage coupling in the d-axis and q-axis coordinate systems based on the rotor current and the phase-locked loop control response characteristics in the d-axis and q-axis coordinate systems includes: When the frequency of the output phase angle disturbance of the phase-locked loop is (ω1-ω er ) is disturbed, the stator voltage in the d-axis and q-axis coordinate systems is coupled based on the output phase angle disturbance of the phase-locked loop and the rotor current in the d-axis and q-axis coordinate systems to obtain a frequency of 2(ω1-ω er ) When the frequency of the output phase angle disturbance of the phase-locked loop is 2(ω1-ω er ) component, based on the grid voltage and the output phase angle disturbance of the phase-locked loop, the grid voltage is coupled to obtain a frequency of n(ω1-ω er )'s frequency multiple.

6. The method according to claim 3, wherein The corresponding voltage disturbance component generated in the rotor voltage command value output by the rotor-side converter is calculated as follows: Where: Δi dr is the rotor d-axis current disturbance component; Δi qr is the rotor q-axis current disturbance component; K p2 K is the RSC current inner loop proportional coefficient; i2 is the RSC current inner loop integral coefficient; Δu dr is the rotor d-axis voltage command disturbance component; Δu qr is the rotor q-axis voltage command disturbance component; The rotor voltage disturbance component is calculated as follows: Where: ω1 is the synchronous speed; ω er is the three-phase voltage frequency; t is the time; U er is the subsynchronous disturbance voltage amplitude; d-axis phase of the voltage disturbance; The q-axis phase of the voltage disturbance.

7. The method according to claim 6, wherein The single-phase disturbance voltage component of the rotor side voltage command value is calculated as follows: Where Δu ar is the single-phase disturbance voltage component of the rotor side voltage command value; ω r is the frequency; U r1 is the frequency (2f1-f r -f er )’s voltage disturbance component amplitude; is the frequency (2f1-f r -f er ) of the voltage disturbance component phase; U r2 is the frequency (f r -f er )’s voltage disturbance component amplitude; is the frequency (f r -f er )’s voltage disturbance component phase.

8. The method according to claim 3, wherein The grid-side converter voltage disturbance component is calculated as follows: Where U g is the amplitude of the disturbance component of the output voltage command value on the GSC side; Δu dg is the d-axis disturbance component of the output voltage command value on the GSC side; Δu qg is the q-axis disturbance component of the output voltage command value on the GSC side; is the phase of the d-axis disturbance component of the output voltage command value on the GSC side; is the phase of the q-axis disturbance component of the output voltage command value on the GSC side; The disturbance voltage of the three-phase voltage on the stator side is calculated as follows: Where Δu as is the disturbance voltage of the three-phase voltage on the stator side; U s1 is the frequency (2f1-f er ) of the stator side voltage disturbance component; is the frequency (2f1-f er ) of the stator side voltage disturbance component phase; U s2 is the frequency f er The amplitude of the stator side voltage disturbance component; is the frequency f er The phase of the stator side voltage disturbance component.

9. The method according to claim 8, wherein The time domain expression of the output phase angle disturbance of the phase-locked loop is shown in the following formula: Where Δθ is the time domain expression of the output phase angle disturbance of the phase-locked loop; u qs is the stator side voltage; K pp is the phase-locked loop proportional coefficient; K pi is the phase-locked loop integral coefficient; The rotor current in the d-axis and q-axis coordinate systems is shown in the following formula: Where: A dr0 is the DC component of the rotor d-axis current; A dr1 is the frequency (f1-f er ) of the rotor d-axis current disturbance component; A dr2 is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component; A qr0 is the DC component of the rotor q-axis current; A qr1 is the frequency (f1-f er ) of the rotor q-axis current disturbance component; A qr2 is the frequency 2(f1-f er ) of the rotor q-axis current disturbance component; is the frequency (f1-f er ) of the rotor d-axis current disturbance component phase; is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component phase; is the frequency (f1-f er ) of the rotor d-axis current disturbance component phase; is the frequency 2(f1-f er ) of the rotor d-axis current disturbance component.

10. A multi-frequency coupling classification system for doubly-fed wind turbines under synchronous disturbances, characterized in that: include: Acquisition module, rule module and determination module; The acquisition module applies different frequencies to the control response of the wind turbine converter to obtain the frequency components generated by the three-phase voltage and current coupling of the doubly-fed wind turbine at different frequencies; The law module is used to obtain the coupling law of the doubly-fed wind turbine generator system based on the components of the frequency generated by the coupling of the three-phase voltage and current of the doubly-fed wind turbine generator system at different frequencies; The determination module determines the frequencies of the three-phase voltage and current of the doubly-fed wind turbine generator set according to the components of the frequencies to be acquired and the coupling law; Wherein, the rule module is used to: When the frequency generated in the stator voltage and current in the three-phase stationary coordinate system is ω er When the disturbance is generated, the stator and rotor voltage and current generation frequency in the synchronous rotating coordinate system is (ω1-ω er )’s disturbance component; When the frequency in the wind turbine converter is (ω1-ω er ) disturbance, the frequency generated by the coupling in the three-phase stator voltage and current of the doubly fed wind turbine is ω er The subsynchronous component and frequency are (2ω1-ω er )'s supersynchronous component; When the phase-locked loop is subjected to subsynchronous disturbance, the coupling frequency in the voltage and current of the doubly fed wind turbine in the synchronous rotating coordinate system is n(ω1-ω er )’s frequency multiplication component; When the coupling in the phase-locked loop generates n(ω1-ω er ) frequency components, the frequency generated by coupling in the three-phase stator voltage and current of the doubly fed wind turbine is n(ω1-ω er )±ω1 components.

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