CN111509767A - High voltage ride through control method for wind power double-fed converter - Google Patents

High voltage ride through control method for wind power double-fed converter Download PDF

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CN111509767A
CN111509767A CN202010186846.4A CN202010186846A CN111509767A CN 111509767 A CN111509767 A CN 111509767A CN 202010186846 A CN202010186846 A CN 202010186846A CN 111509767 A CN111509767 A CN 111509767A
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voltage
current
grid
bus
converter
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CN111509767B (en
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马强
武鑫
吕佃顺
王立鹏
王朝
孙明丽
冯莉
许洪华
赵栋利
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Jiangsu Guoke Intelligent Electric Co ltd
Corona Wind Energy Equipment Beijing Co ltd
Beijing Corona Science and Technology Co Ltd
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Jiangsu Guoke Intelligent Electric Co ltd
Corona Wind Energy Equipment Beijing Co ltd
Beijing Corona Science and Technology Co Ltd
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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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • 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
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • 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
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

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  • Power Engineering (AREA)
  • Control Of Eletrric Generators (AREA)

Abstract

A high voltage ride through control method for a wind power double-fed converter is characterized in that when the voltage of a power grid is increased to 1.1-1.3 times of a nominal voltage, an optimized phase-locked loop technology is used, a grid-side converter prevents overmodulation through flexible control of direct-current bus voltage, and a machine side outputs inductive reactive current to reduce the voltage amplitude of the power grid. By using the method, the converter can continuously run without disconnecting the network under the condition that the voltage of the power grid is 1.1-1.3 times of the nominal voltage without complicated mode switching and hardware cost increase, and inductive reactive power output meeting the national standard is provided.

Description

High voltage ride through control method for wind power double-fed converter
Technical Field
The invention relates to a control method of a wind power double-fed converter.
Background
In recent years, the problem of high voltage ride through of wind power plants is more and more emphasized, and a high-ride-through standard GB/T36995-2018 wind generating set fault voltage ride through capability test rule is issued 7 months in 2019.
The high penetration standard requires: when the voltage of a grid-connected point of a wind power plant is increased to 1.3 times of the nominal voltage, the wind turbine generator can continuously run for 500ms without being disconnected; when the voltage is increased to 1.25 times of the nominal voltage, the system can continuously run for 1s without disconnecting the network; when the voltage is increased to 1.2 times of the nominal voltage, the continuous operation for 10s without network disconnection should be realized; at 1.1 times the nominal voltage, the wind turbine should be able to operate continuously. And the wind turbine generator can provide extra reactive support to assist the voltage recovery of the power grid.
For the doubly-fed converter, the transient process of the rise and the fall of the grid voltage can cause the magnetic flux linkage of the stator to oscillate greatly, and the direct current component and the negative sequence component induce high voltage on the rotor under the condition of high slip ratio, which may cause the loss control of a current controller of the machine side converter. For the grid-side converter, the grid voltage rise will directly cause the occurrence of the over-modulation condition, and part of the energy will flow from the grid to the direct current bus side uncontrollably, resulting in a sharp rise in the direct current bus voltage. The unit without high voltage ride through capability will have over-current and over-voltage fault shutdown.
The high voltage ride through is a key technology of subject research, and the high voltage ride through control method of the double-fed converter can solve the problem of out-of-control over modulation current in the high voltage ride through and meet the requirement of reactive power standard.
In order to realize high voltage ride through, patent CN201710288009 discloses a method for controlling a doubly-fed converter at a high voltage ride through side, which proposes a method for controlling a converter at a side, but does not propose a control strategy of a grid-side converter for a dc bus voltage, so that current runaway at the grid side due to overmodulation cannot be solved, and active power output is reduced and power generation is lost during a voltage rising steady state period due to an unloading action in the voltage rising steady state process, so that the requirement for a high pass standard power fluctuation error issued in 2019 may not be met due to excessive limitation of the active current output at the side.
Disclosure of Invention
The invention provides a high voltage ride through control method of a double-fed converter, aiming at overcoming the defect that the conventional double-fed converter control method cannot meet the high voltage ride through requirement. The invention can solve the problem of out-of-control over-modulation current in high voltage ride through and simultaneously meet the reactive power requirement of a power grid.
For a double-fed converter, the machine side is the core for controlling active power and reactive power, so the method for restraining the grid voltage rise mainly depends on the machine side. The premise that the voltage of the direct current bus is stable is that the voltage of the direct current bus is stable, and the premise that the voltage of the direct current bus is stable is that the over-modulation operation of the grid side is prevented, so that the machine-side converter and the grid-side converter need to work in a matched mode. And the network side should adopt an active power priority control strategy to keep the stability of the direct current bus voltage. The machine side generates inductive reactive power by controlling rotor excitation, and the surplus capacity maintains enough torque output, thereby inhibiting the overspeed of the generator.
The control method is realized through the combined action of the network side converter and the machine side converter, and specifically comprises the following steps:
(1) control strategy one, changing given value of network side direct current bus voltage
When the voltage of a power grid rises, the maximum threat of current stability control is overmodulation, because in an overmodulation state, the power grid injects uncontrollable active current into a direct current side, so that current harmonics on the power grid side are increased, the voltage of a direct current bus is unstable, and active and reactive current control on the power grid side is influenced. In order to solve the problem, the invention changes the given value U of the DC bus voltage according to the rising amplitude of the grid voltagedcset：
Udcset＝Udcbase+Udck×(UT-Udcb)，UdcMin<Udcset<UdcMax
In the formula of UTIs the per unit value of the positive sequence voltage of the power grid, UdcbaseIs a given value of DC bus voltage U when the grid voltage is normaldckFor adjusting the coefficient of DC bus voltage, UdcbAdjusting bias, U, for DC bus voltagedcMinMinimum value of DC bus voltage allowed for safe operation, UdcMaxMaximum dc bus voltage allowed for safe operation.
(2) A second control strategy is to adopt network side active current priority control
In order to stabilize the direct-current bus voltage, the grid-side converter operates in an active priority mode under the condition of total current limitation, and unloading does not need to be carried out during the period that high voltage crosses a steady state. The network side converter preferentially meets the requirement of active current, then the maximum reactive current given value is obtained through the square difference, and the maximum reactive current given value is used as the amplitude limiting value of the reactive current given value.
When the per unit value range of the positive sequence voltage of the power grid is more than or equal to U (1.1)TWhen the maximum reactive current is less than or equal to 1.3, the maximum reactive current set value IndMaxThe following equation is obtained:
Figure BDA0002414498530000021
in the formula InnFor rated current of grid-side converter, InqIs the net side active current.
(3) And thirdly, dynamically adjusting the unloading switching hysteresis threshold value of the network side
The transient process of voltage rise and recovery has current impact, which may cause overvoltage of the direct current bus, and at this time, unloading suppression is generally adopted: when the voltage of the direct current bus is greater than a set threshold value UdccutinUnloading when the DC bus voltage is less than a set threshold UdccutoutUnloading is carried out in a time-out mode, and a hysteresis loop is arranged between two threshold values. This fixed switching threshold approach is not applicable under flexible control of dc bus voltage. The control method of the invention combines the given value of the DC bus voltage obtained by the first control strategy to provide an unloading switching method as follows:
the unloading input conditions are as follows: the voltage of the DC bus is greater than the input threshold value UdccutinAnd the DC bus voltage is greater than the given value U of the DC bus voltagedcsetAnd a set margin Δ UdcMaxThe sum of (1).
The unloading and cutting conditions are as follows: the DC bus voltage is less than the cut-out threshold value UdccutoutOr the DC bus voltage is less than the given value U of the DC bus voltagedcsetAnd a set margin Δ UdcMaxThe sum of (1).
ΔUdcMaxDescription of the drawings: delta UdcMax＝Udck×(UT-Udcb)
In the formula of UTIs the per unit value of the positive sequence voltage of the power grid, UdckFor adjusting the coefficient of DC bus voltage, UdcbThe bias is adjusted for the dc bus voltage.
In the transient state of the rise of the power grid voltage, because the given value threshold value of the direct current bus voltage is relatively low, unloading can be quickly carried out to restrain overvoltage, and unnecessary active power can be prevented from being consumed by unloading during the steady state of the rise of the power grid voltage.
(4) Control strategy four, improve the control of the phase-locked loop of network side
Decoupling control is introduced into the network side phase-locked loop, so that response lag generated by phase shift of 90 degrees used in positive and negative sequence separation of a symmetric component method is avoided. Compared with a symmetric component method, harmonic components in the positive-negative sequence DQ axis voltage are filtered out due to the existence of the low-pass filter. The method performs per unit processing on the input of the phase-locked loop front-end controller, so that the angular speed output has approximate response speed under the condition of different grid voltage amplitudes. And the frequency output is more stable due to the slope and low pass filtering.
(5) Control strategy five, priority control machine side reactive current
The machine side converter runs in a reactive power priority mode to generate inductive reactive power and inhibit the voltage of the power grid from rising; the remaining capacity maintains sufficient torque output to suppress generator overspeed.
In the transient process of the voltage rise and recovery of a power grid, because a rotor is cut at a high speed by a direct current component attenuated in a stator flux linkage and a stator flux linkage negative sequence component generated by voltage unbalance, the voltage of the rotor is vibrated and raised, and further overcurrent is caused.
When the per unit value range of the positive sequence voltage of the power grid is more than or equal to U (1.1)TWhen the current is less than or equal to 1.3, the reactive current IdIn accordance with the following formula,
Id≤-1.5×(UT-1.1)×IN
in the formula INRated current, U, of the wind turbineTAnd the voltage per unit value of the positive sequence of the power grid.
The negative sign in the above formula represents the reactive current IdIs inductive, i.e. reactive. Maximum active current given value IqMaxThe following formula was used to obtain,
Figure BDA0002414498530000031
in the formula IsThe maximum current of the converter.
The machine side and the network side of the invention are applied to the converter, and the five control strategies are not in sequence, so that the high voltage ride through function of the double-fed converter can be realized.
At present, the double-fed converter is generally provided with a low-voltage ride-through component, so that the control method can realize a high-voltage ride-through function of not more than 1.3 times of the nominal voltage under the condition of keeping the original hardware unchanged, and save the hardware upgrading cost.
Drawings
FIG. 1 is a topology diagram of a doubly-fed converter;
FIG. 2 is a block diagram of an improved phase-locked loop decoupling unit;
FIG. 3 is a block diagram of an improved PLL control algorithm;
fig. 4a and 4b are simulation waveforms of a 1.5MW doubly-fed converter when the grid voltage is increased to 1.3 times in balance and increased to 1.3 times in unbalance.
Detailed Description
The invention is further described below with reference to the accompanying drawings and the detailed description.
As shown in fig. 1, a main circuit of the doubly-fed converter of the present invention is composed of a grid-side converter 101, a machine-side converter 102, and a dc-off load 103, where the grid-side converter 101 and the machine-side converter 102 are connected through a dc side, the dc-off load 103 is connected to a positive pole and a negative pole of the dc side, and a master controller 111 includes two parts, namely a grid-side controller and a machine-side controller, and respectively controls the grid-side converter 101 and the machine-side converter 102.
The network side current controller is of a double-ring structure, the given value of the outer ring of the direct current bus voltage subtracts a direct current bus voltage feedback value from the given value of the direct current bus voltage to obtain direct current bus voltage deviation, and the given value of the active current is output through the PI regulator. The active current set value is used as the input of the current controller. The reactive current given value directly enters the current controller from the reactive current given value. The phase-locked loop is used for extracting the voltage sequence component of the power grid, obtaining a positive sequence voltage angle and supplying the positive sequence voltage angle to the current controller for use. The machine side controller is based on a stator flux linkage directional vector control technology and completes machine side active and reactive current decoupling control.
In a conventional control method, a given value of the direct-current bus voltage is a constant. In the invention, the given value of the direct current bus voltage is changed according to the rising amplitude of the power grid voltage, and is obtained by the following formula,
Udcset＝Udcbase+Udck×(UT-Udcb)，UdcMin<Udcset<UdcMax
in the formula of UTIs the per unit value of the positive sequence voltage of the power grid, UdcbaseIs a given value of DC bus voltage U when the grid voltage is normaldckFor adjusting the coefficient of DC bus voltage, UdcbAdjusting bias, U, for DC bus voltagedcMinMinimum value of DC bus voltage allowed for safe operation, UdcMaxMaximum dc bus voltage allowed for safe operation.
Taking a 1.5MW doubly-fed converter as an example, the dc-side capacitance voltage rating is usually 1100V, and 1.15 times the overvoltage: 1265V can endure 30 minutes at the longest and does not influence service life, and when the grid voltage is normal, the given value U of the DC bus voltagedcbaseThe maximum set value U of the DC bus voltage allowed by safe operation is set to 1065VdcMaxSet to 1200V. When the grid voltage is at 1.1 times of rated value, the converter can operate for a long time, and the given value U of the DC bus voltage is calculateddcset1090V, less than the rated voltage of the capacitor, and meets the requirement of long-time operation.
In order to stabilize the dc bus voltage, the grid-side converter operates in an active priority mode. The grid-side converter preferentially meets the requirement of active current, then the maximum reactive current given value is obtained through the square difference under the condition of total current limitation, and the value is used as the amplitude limit value of the reactive current given value.
As described above, the given value of the dc bus voltage is dynamically calculated during the high voltage period, and in order to improve the unloading response speed and ensure that the dc bus voltage is at a higher given value position to avoid the unloading action, the dynamic adjustment network side unloading switching hysteresis threshold strategy of the present invention is as follows:
the unloading input conditions are as follows: the voltage of the DC bus is greater than the input threshold value UdccutinAnd the DC bus voltage is greater than the given value U of the DC bus voltagedcsetAnd a set margin Δ UdcMaxThe sum of (1).
The unloading and cutting conditions are as follows: the DC bus voltage is less than the cut-out threshold value UdccutoutOr the DC bus voltage is less than the given value U of the DC bus voltagedcsetAnd a set margin Δ UdcMaxThe sum of (1).
Taking a 1.5MW doubly-fed converter as an example, considering that the overvoltage value of 1.15 times of the DC bus capacitor is 1265V, the DC bus voltage is set to be margin delta U in the formula when the load is unloaded and the DC bus voltage is completely put into usedcMaxSet to 60V, general UdccutinAnd UdccutoutAre all less than Udcset+ΔUdcMax。
Fig. 2 is a block diagram of an improved phase-locked loop decoupling unit. Assuming a positive sequence reference coordinate system dqpAngular velocity position and positive sequence voltage magnitude vpWhen the angles are overlapped, θ' is ω t, and ω is the grid angular frequency, the input voltage vector can be expressed by the following formula under the positive sequence coordinate system and the negative sequence coordinate system.
Figure BDA0002414498530000051
Figure BDA0002414498530000052
In the formula:
Figure BDA0002414498530000053
in order to transform the matrix in-between,
Figure BDA0002414498530000054
for the positive sequence voltage vector reference to be,
Figure BDA0002414498530000055
is a negative sequence voltage vector reference and,
Figure BDA0002414498530000056
is a positive sequence voltage d-axis vector reference,
Figure BDA0002414498530000057
for a positive sequence voltage q-axis vector reference,
Figure BDA0002414498530000058
is a negative sequence voltage d-axis vector reference,
Figure BDA0002414498530000059
for negative sequence voltage q-axis vector reference, vαβIs the voltage transformed by αβ coordinate system.
It can be seen that dqpAnd dqnThe DC component in the coordinate system corresponds to the amplitude V of the positive sequence component and the negative sequence component of the input signal respectivelypAnd Vn。
As shown in the above formula, in dqpThe magnitude of the alternating component of the axis being dependent on dqnThe direct current component on the shaft and vice versa. It is assumed that the pre-estimated DC component is represented as
Figure BDA00024144985300000510
The phase-locked loop angle is represented as theta, then the d-axis positive sequence can be decoupled by using the decoupling unit shown in fig. 2, and the other 3 components have the same form.
Fig. 3 is a block diagram of the improved pll control algorithm of the present invention. Network voltage vabcThe voltage transformed into αβ coordinate system is denoted as vαβ(ii) a After the power grid angle theta is obtained, the voltage is converted by the decoupling unit to obtain a positive sequence voltage reference which is recorded as
Figure BDA0002414498530000061
Voltage reference for controller
Figure BDA0002414498530000062
And L PF filtered negative sequence coordinate system voltage
Figure BDA0002414498530000063
The decoupling conversion value of (a) is subtracted to obtain an error signal
Figure BDA0002414498530000064
Is processed by per unit to obtain
Figure BDA0002414498530000065
Entering a PI regulator; and outputting by the regulator to obtain the grid angular frequency omega, and further calculating the grid angle theta.
After the current controller obtains the current signal, positive and negative sequence separation is carried out through a power grid angle theta output by the phase-locked loop, the separated sequence components are input into the PI regulator, the positive sequence current controller outputs positive sequence voltage, the negative sequence current controller outputs negative sequence voltage and simultaneously enters an SVPWM (space vector pulse width modulation) debugging algorithm, and the IGBT of the power unit is driven to act.
The machine side converter runs in a reactive power priority mode to generate inductive reactive power and inhibit the voltage of the power grid from rising; the maximum current of the converter is limited by the capacity, the residual capacity maintains enough torque output, and the square sum of the active current and the reactive current is not larger than the square of the total current.
Taking 1.5MW doubly-fed converter as an example, the rated current IN1050A, the reactive current setpoint may be obtained by,
Id＝-1.5×(UT-1.1)×INand the negative sign is reactive power absorption.
The per-unit value of the total current of the converter can reach 1.1, and the per-unit value of the output active power is obtained
Figure BDA0002414498530000066
In the limited range of 1.1 ≦ UTLess than or equal to 1.3, PpuConstantly greater than 1, indicates that the increase in the grid voltage does not affect the rated active power output even in the reactive priority mode. So no action is required for unloading and Crowbar during high-penetration steady state.
Assuming that the maximum current of the converter is IsMaximum active current set value IqMaxThe following formula was used to obtain,
Figure BDA0002414498530000067
taking a 1.5MW doubly-fed converter as an example, the control method is verified through simulation. The simulation result of the grid voltage balance increased to 1.3 times when the converter operates at rated power is shown in fig. 4 a. In fig. 4a, the grid voltage Vgabc is increased in balance, the current control effect is gradually improved in the high-voltage period of the grid current Igabc, and the overall effect is better; the active power and the reactive power of the power grid meet the national standard requirements. The simulation result of the grid voltage unbalance increased to 1.3 times when the converter operates at rated power is shown in fig. 4 b. In fig. 4b, the grid voltage Vgabc rises in an unbalanced manner, and the total current control effect is better when the grid current Igabc is in a high-voltage period; the active power of the power grid meets the national standard requirements, and extra reactive power is supported and output.

Claims (8)

1. A high voltage ride through control method of a wind power double-fed converter is characterized by comprising the following steps: the control method is realized by the combined action of the following five control strategies:
strategy one, changing a given value of the voltage of a direct current bus at the network side;
strategy two, adopting network side active current priority control;
a third strategy is to dynamically adjust the unloading switching hysteresis threshold value of the network side;
strategy four, improving network side phase-locked loop control;
and a fifth strategy is to preferentially control the machine side reactive current.
2. The wind power double-fed converter high voltage ride through control method according to claim 1, characterized in that: when the voltage of the power grid rises, the maximum threat of current stability control is overmodulation, and according to the strategy I, the given value U of the voltage of a direct-current bus on the grid side is changed according to the rising amplitude of the voltage of the power griddcset，
Udcset＝Udcbase+Udck×(UT-Udcb)，UdcMin<Udcset<UdcMax
In the formula of UTIs the per unit value of the positive sequence voltage of the power grid, UdcbaseIs a given value of DC bus voltage U when the grid voltage is normaldckFor adjusting the coefficient of DC bus voltage, UdcbAdjusting bias, U, for DC bus voltagedcMinMinimum value of DC bus voltage allowed for safe operation, UdcMaxMaximum dc bus voltage allowed for safe operation.
3. The wind power double-fed converter high voltage ride through control method according to claim 1, characterized in that: the method for the network side active current priority control of the strategy two comprises the following steps: in order to stabilize the voltage of the direct-current bus, the grid-side converter preferably meets the requirement of active current, then the maximum reactive current given value is obtained through the square difference, and the maximum reactive current given value is used as the amplitude limiting value of the reactive current given value.
4. The wind power doubly-fed converter high voltage ride through control method of claim 3, characterized in that: the maximum reactive current given value IndMaxThe following formula was used to obtain,
Figure FDA0002414498520000011
in the formula InnFor rated current of grid-side converter, InqIs the net side active current.
5. The wind power double-fed converter high voltage ride through control method according to claim 1, characterized in that: the method for dynamically adjusting the unloading switching hysteresis threshold of the network side in the strategy III comprises the following steps: in the transient process of the voltage rise and recovery of the power grid, the overvoltage of the direct-current bus is restrained by switching unloading;
the unloading input conditions are as follows: the voltage of the DC bus is greater than the input threshold value UdccutinAnd the DC bus voltage is greater than the given value U of the DC bus voltagedcsetAnd a set margin Δ UdcMaxThe sum of (1);
the unloading and cutting conditions are as follows: the DC bus voltage is less than the cut-out threshold value UdccutoutOr the DC bus voltage is less than the given value U of the DC bus voltagedcsetAnd a set margin Δ UdcMaxThe sum of (1).
6. The wind power double-fed converter high voltage ride through control method according to claim 1 is characterized in that a decoupling network is introduced into a phase-locked loop according to the improved network side phase-locked loop control algorithm of the strategy IV, response lag generated by phase shifting 90 degrees used in the positive and negative sequence separation of a symmetric component method is avoided, L PF filtering is used for filtering harmonic components in positive and negative sequence DQ axis voltage, and per unit processing is performed on PI input at the front end of the phase-locked loop, so that angular speed output has approximate response speed under the condition of different grid voltage amplitudes.
7. The wind power doubly-fed converter high voltage ride through control method of claim 6, characterized in that: the improved network side phase-locked loop control algorithm is as follows:
(1) network voltage vabcThe voltage transformed into αβ coordinate system is denoted as vαβ；
(2) After the power grid angle theta is obtained, the voltage is converted by the decoupling unit to obtain a positive sequence voltage reference which is recorded as
Figure FDA0002414498520000021
(3) Voltage reference for controller
Figure FDA0002414498520000022
And L PF filtered negative sequence coordinate system voltage
Figure FDA0002414498520000023
The decoupling conversion value of (a) is subtracted to obtain an error signal
Figure FDA0002414498520000024
Is processed by per unit to obtain
Figure FDA0002414498520000025
Entering a PI regulator;
(4) the PI regulator outputs to obtain a power grid angular frequency omega, and then a power grid angle theta is calculated;
(5) after the current controller obtains the current signal, positive and negative sequence separation is carried out through a power grid angle theta output by the phase-locked loop, the separated sequence components are input into the PI regulator, the positive sequence current controller outputs positive sequence voltage, the negative sequence current controller outputs negative sequence voltage and simultaneously enters an SVPWM (space vector pulse width modulation) debugging algorithm, and the IGBT of the power unit is driven to act.
8. The wind power double-fed converter high voltage ride through control method according to claim 1, characterized in that: the method for preferentially controlling the machine side reactive current of the strategy five comprises the following steps: the machine side converter runs in a reactive power priority mode to generate inductive reactive power and inhibit the voltage of the power grid from rising; the surplus capacity maintains enough torque output, and the generator is restrained from overspeed;
maximum active current given value IqMaxThe following formula was used to obtain,
Figure FDA0002414498520000026
in the formula IsIs the maximum current of the converter, IdIs a reactive current, UTIs the per unit value of the positive sequence voltage of the power grid, INThe rated current of the wind turbine generator is obtained.
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CN113258585A (en) * 2021-05-14 2021-08-13 明阳智慧能源集团股份公司 Wind turbine generator system fault voltage ride-through reactive power control method, system, medium and equipment

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