CN115085250A - Low voltage ride through control method for direct-drive fan and related equipment - Google Patents

Low voltage ride through control method for direct-drive fan and related equipment Download PDF

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Publication number
CN115085250A
CN115085250A CN202210545507.XA CN202210545507A CN115085250A CN 115085250 A CN115085250 A CN 115085250A CN 202210545507 A CN202210545507 A CN 202210545507A CN 115085250 A CN115085250 A CN 115085250A
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voltage
low
value
ride
direct
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马遵
何鑫
何廷一
邓灿
许珂玮
奚鑫泽
邢超
李胜男
马红升
和鹏
孟贤
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Electric Power Research Institute of Yunnan Power Grid Co Ltd
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Electric Power Research Institute of Yunnan Power Grid 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
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • 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
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
    • 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

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

Abstract

The embodiment of the invention discloses a low voltage ride through control method of a direct-drive fan and related equipment. The method comprises the following steps: under the condition that the low voltage ride through triggering module detects that the current voltage value of a target power grid where the target direct drive fan is located is lower than a preset reference value, generating a ride through high level signal to activate a low voltage ride through mode; calculating the voltage drop depth according to the current voltage value and the preset reference value; a reactive power control module of the network side control system in a low voltage period controls the target direct-drive fan to output reactive power to the target power grid according to the voltage drop depth so as to support the power grid; and the active control module controls the output power of the target direct-drive fan according to the voltage drop depth during the low voltage ride through period of the machine side control system. The direct-drive fan low-voltage ride-through control method overcomes the defect of direct-current voltage overvoltage oscillation in the prior art, and limits the machine side electromagnetic power of the fan during low-ride-through period from the source.

Description

Low voltage ride through control method for direct-drive fan and related equipment
Technical Field
The invention relates to the field of power electronic technology control, in particular to a low voltage ride through control method and related equipment for a direct-drive fan.
Background
The method has the advantages that single-phase faults and three-phase faults occur occasionally in the power system, the wind generation sets are guaranteed to operate without being disconnected when a power grid fails along with large-scale wind generation sets in a grid-connected mode, and especially in the period of low voltage of the power grid, the problem that the improvement of the low voltage ride through capability of the wind generation sets under the faults is needed to be solved urgently at present. The existing direct-drive fan low-voltage ride through control method mainly aims at fan grid-side converter control.
The output power of the machine side converter and the output power of the grid side converter of the direct-drive fan are calculated according to a formula
Figure BDA0003652370960000011
And performing power flow control, and if the grid-side converter cannot send active power, causing the rise of the direct-current voltage to exceed the limit. In a general direct-drive fan low-voltage ride-through control method, when the voltage of a power grid drops, constant reactive power control of a grid-side converter is switched to low-ride-through reactive current control responding to the voltage change of the power grid, the grid-side converter adopts a strategy of maintaining active power or current, but does not limit the output power of the machine-side converter, and therefore the problems that the direct-current voltage of the converter during low-voltage ride-through is high in amplitude oscillation and the stability of the direct-current voltage is poor are caused.
Disclosure of Invention
In this summary, concepts in a simplified form are introduced that are further described in the detailed description. This summary of the invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In order to improve the control link of a grid-side converter and a machine-side converter of a direct-drive fan and ensure safe and reliable operation of the direct-drive fan during low voltage ride through, on the first aspect, the invention provides a low voltage ride through control method of the direct-drive fan, which comprises the following steps:
under the condition that a low voltage ride through trigger module detects that the current voltage value of a target power grid where a target direct-drive fan is located is lower than a preset reference value, generating a ride through high level signal to activate a low voltage ride through mode, wherein a direct-drive fan low voltage ride through control system comprises a grid side control system and a machine side control system, in the low voltage ride through mode, a reactive power control module of the grid side control system is closed in a voltage normal period and works in a low voltage period, and an active power control module of the machine side control system is closed in a voltage normal period and works in a low voltage ride through period;
calculating the voltage drop depth according to the current voltage value and the preset reference value;
a reactive power control module of the network side control system in a low voltage period controls the target direct-drive fan to output reactive power to the target power grid according to the voltage drop depth so as to support the power grid;
and the active control module controls the output power of the target direct-drive fan according to the voltage drop depth during the low voltage ride through period of the machine side control system.
Optionally, the low voltage ride through trigger module includes an effective value calculator, a first-order hysteresis device, and a comparator;
the effective value calculator is used for calculating the effective value of the three-phase alternating voltage of the bus bar after the phase change boosting of the target direct-drive fan;
the first-order hysteresis device is used for carrying out low-pass filtering on the effective value of the three-phase alternating voltage of the bus bar;
the comparator is used for outputting the higher level signal when the effective value of the three-phase alternating voltage of the bus bar is lower than a preset low voltage crossing threshold value.
Optionally, the step of controlling, by the reactive power control module of the grid-side control system during the low voltage period, the target direct-drive fan to output reactive power to the target grid according to the voltage drop depth to support the grid includes:
and the reactive power control module of the network side control system in the low voltage period calculates the reactive current corresponding to the reactive power according to the voltage drop depth by the following formula:
i ds_ref ＝1.5×(0.9-U pcc_pu )×1.1
in the formula i ds_ref Is a reactive current, 0.9-U pcc_pu To a voltage dropAmplitude of fall, U pcc_pu The effective value of the three-phase alternating voltage of the bus is obtained;
and controlling the target direct-drive fan to output the reactive current to the target power grid so as to support the power grid.
Optionally, the method further includes:
the low voltage ride through trigger module generates a low level recovery signal to activate a voltage recovery mode when detecting that the current voltage value of the target power grid is recovered to be greater than or equal to the preset reference value, wherein in the voltage recovery mode, a reactive power control module of the network side control system works in a normal voltage period and is closed in a low voltage period, and a power control module of the machine side control system works in the voltage recovery period and is closed in the low voltage ride through period;
the reactive power control module controls the target direct-drive fan to preferentially output active power to the target power grid during the voltage normal period of the grid-side control system;
and when the voltage of the machine side control system is recovered, the power control module controls the output power of the target direct-drive fan to be increased to a rated value according to the fixed increasing speed.
Optionally, the method further includes:
under the condition that the current voltage value is recovered to be greater than or equal to the preset reference value, the target direct-drive fan controls power according to the following formula:
T e ＝1.5pΨ f i q
in the formula: t is e For the direct-drive fan electromagnetic torque, p represents the pole pair number psi f For directly driving the rotor flux linkage i of the fan q Is the component of the direct drive fan stator current on the q axis.
Optionally, the active control module during the low voltage ride through period includes an adder and a limiter;
the adder is used for calculating the difference value between the target power grid voltage and a preset reference value;
the limiter is used to limit the adder output value within an acceptable range.
Optionally, the voltage recovery power control module includes a sample holder, an or gate, a first adder, a divider, a pulse generator, a not gate, an integrator, and a second adder;
the sampling holder is used for locking an active current value of an inner ring of the machine side converter entering low penetration when the voltage of a target power grid is not recovered to a preset reference value or the active power output by the fan side is not recovered to a rated value;
the first adder is used for calculating a difference value between an active current instruction value in a low voltage ride through mode and an active current value of an inner ring of the fan-side converter;
under the voltage recovery mode, the pulse generator receives and recovers a low level signal through an input end and sends out a high level signal with the time length being the output value of the divider through an output end;
the NOT gate is used for keeping a low-level signal in the voltage recovery mode;
the integrator is used for integrating according to a fixed slope value and outputting an inner loop active current instruction change value in a voltage recovery period;
the second adder is used for summing the inner-loop active current instruction change value output by the integrator and the active current instruction value in the low-voltage ride-through mode to obtain the active current instruction in the voltage recovery mode.
In a second aspect, the present invention further provides a direct drive fan low voltage ride through control device, including:
the direct-drive fan low-voltage ride-through control system comprises a grid-side control system and a machine-side control system, wherein in the low-voltage ride-through mode, a reactive power control module of the grid-side control system is closed in a voltage normal period and works in a low-voltage period, and an active power control module of the machine-side control system is closed in a voltage normal period and works in a low-voltage ride-through period;
the calculating unit is used for calculating the voltage dropping depth according to the current voltage value and the preset reference value;
the first control unit is used for controlling the target direct-drive fan to output reactive power to the target power grid according to the voltage drop depth so as to support the power grid;
and the second control unit is used for controlling the output power of the target direct-drive fan according to the voltage drop depth.
In a third aspect, the present invention further provides a direct drive fan low voltage ride through control system, which can implement any one of the direct drive fan low voltage ride through control methods described in the first aspect, and includes: the device comprises a low voltage ride through triggering module, a reactive power control module in a voltage normal period, a reactive power control module in a low voltage period, an active power control module in a voltage normal period, an active power control module in a low voltage ride through period and an active power control module in voltage recovery.
In a fourth aspect, the present invention further provides a direct drive fan, including the direct drive fan low voltage ride through control system in the third aspect.
The embodiment of the invention has the following beneficial effects:
the direct-drive fan low-voltage ride-through control method overcomes the defect of direct-current voltage overvoltage oscillation in the prior art, and the direct-drive fan can provide reactive support for a power grid during a low-voltage period and ensure the stability of direct-current voltage by comprehensively considering the control systems of the grid side converter and the machine side converter of the direct-drive fan. According to the method, the active current instruction value of the machine side in the low-penetration period is quickly adjusted according to the change of the voltage of the power grid, and the electromagnetic power of the machine side in the low-penetration period of the fan is limited from the source. The problems of unbalance of active power of the network side and the machine side, overcharge of a direct current capacitor and direct current voltage oscillation during low-pass are avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Wherein:
fig. 1 is a schematic flow chart of a direct drive fan low voltage ride through control method according to an embodiment of the present application;
fig. 2 is a schematic power flow diagram of a direct-drive wind turbine provided in an embodiment of the present application;
fig. 3 is a schematic structural diagram of a direct drive fan low voltage ride through control system according to an embodiment of the present application;
fig. 4 is a simulation control block diagram of a low voltage ride through trigger module RTDS of a direct drive fan grid-side converter control system according to an embodiment of the present application;
fig. 5 is a simulation control block diagram of a reactive power control module RTDS during a low voltage period of a direct drive wind turbine grid-side converter control system according to an embodiment of the present application;
fig. 6 is a simulation control block diagram of an active power control module RTDS during a low voltage ride through period of a direct drive fan machine side converter control system according to an embodiment of the present application;
fig. 7 is a simulation control block diagram of an RTDS when voltage of a direct-drive fan machine side converter control system recovers according to the embodiment of the present application;
fig. 8 is a schematic diagram of a simulation test waveform of a direct-drive fan for low voltage ride through RTDS according to an embodiment of the present application;
FIG. 9 is a diagram illustrating simulation results of controlling the DC voltage RTDS by the method of the present application according to an embodiment of the present application;
FIG. 10 is a comparison graph of simulation of controlling the DC voltage RTDS by a conventional method according to an embodiment of the present application;
fig. 11 is a graph of a simulation result of controlling the dq-axis inner loop current RTDS of the dc-side converter by using the method of the present application according to the embodiment of the present application;
fig. 12 is a graph of a simulation result of controlling the dq-axis inner loop current RTDS of the dc-side converter by using the existing method according to the embodiment of the present application;
fig. 13 is a schematic structural diagram of a low-voltage ride-through control device of a direct-drive fan according to an embodiment of the present application;
fig. 14 is a schematic structural diagram of the direct drive fan low voltage ride through control electronic device according to the embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terms "first," "second," "third," "fourth," and the like in the description and in the claims of the present application and in the drawings described above, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It will be appreciated that the data so used may be interchanged under appropriate circumstances such that the embodiments described herein may be practiced otherwise than as specifically illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus. The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments.
Referring to fig. 1, a schematic flow chart of a direct drive fan low voltage ride through control method provided in an embodiment of the present application may specifically include:
s110, generating a ride-through high-level signal to activate a low-voltage ride-through mode under the condition that a low-voltage ride-through trigger module detects that the current voltage value of a target power grid where a target direct-drive fan is located is lower than a preset reference value, wherein the direct-drive fan low-voltage ride-through control system comprises a grid-side control system and a machine-side control system, in the low-voltage ride-through mode, a reactive power control module of the grid-side control system is closed in a voltage normal period and a reactive power control module of the grid-side control system works in a low-voltage period, and an active power control module of the machine-side control system is closed in a voltage normal period and works in a low-voltage ride-through period;
s120, calculating a voltage drop depth according to the current voltage value and the preset reference value;
s130, a reactive power control module of the network side control system in a low voltage period controls the target direct-drive fan to output reactive power to the target power grid according to the voltage drop depth so as to support the target power grid;
and S140, controlling the output power of the target direct-drive fan by the active control module during the low voltage ride through period of the machine side control system according to the voltage drop depth.
For example, as shown in fig. 2, a power flow diagram of a direct-drive wind turbine is shown, the direct-drive wind turbine converts mechanical energy into electrical energy by capturing wind energy, and the electrical energy is transmitted to a power grid by the conversion of a machine side converter and a grid side converter. Fig. 3 is a schematic structural diagram of a direct drive fan low voltage ride through control system, which includes: the system comprises a low voltage ride through trigger module, a reactive power control module in a low voltage period and a reactive power control module in a voltage normal period of a grid-side converter control system, and an active power control module in a low voltage ride through period, an active power control module in voltage recovery and an active power control module in a voltage normal period of a machine-side converter control system. When the power grid fails, the low voltage ride through triggering module detects the voltage drop of the power grid, a triggered high level signal (i.e. ride through high level signal) is generated, and the fan enters a low voltage ride through mode. The direct-drive fan grid-side converter control system (namely a grid-side control system) is switched from a reactive control module in a grid normal period to a reactive control module in a low voltage period (namely the reactive control module in the grid-side control system is closed in the voltage normal period and works in the low voltage period), the reactive current instruction Ids _ ref value of the grid-side converter is adjusted according to the voltage drop depth, reactive power is preferentially output to the grid side, and the grid voltage is supported. Meanwhile, the active control module of the direct-drive fan side converter control system is controlled to be switched to the active control module during low voltage ride through (namely the active control module of the fan side control system is closed during normal voltage and the active control module works during low voltage ride through), the active current instruction Iqr _ ref value of the fan side converter is adjusted according to the voltage drop amplitude of the grid side, the torque current of the fan side is rapidly reduced, and the electromagnetic power of the fan side is limited, so that the output power of the fan side is reduced, the problem that direct-current overvoltage oscillation is caused by overcharge of a direct-current capacitor during fault is avoided, and the direct-drive fan grid side control system (namely the grid side control system) comprises a fan side converter.
In summary, the method provided by the embodiment of the application overcomes the defect of direct-current voltage overvoltage oscillation in the prior art, and the direct-drive fan can provide reactive support for a power grid during a low-voltage period and ensure the stability of direct-current voltage by comprehensively considering the control systems of the grid side converter and the machine side converter of the direct-drive fan. According to the method, the active current instruction value of the machine side in the low-penetration period is quickly adjusted according to the change of the voltage of the power grid, and the electromagnetic power of the machine side in the low-penetration period of the fan is limited from the source. The problems of unbalance of active power of the network side and the machine side, overcharge of a direct current capacitor and direct current voltage oscillation during low-pass are avoided.
In some embodiments, the low voltage ride through trigger module includes an effective value calculator, a first-order hysteresis device, and a comparator;
the effective value calculator is used for calculating the effective value of the three-phase alternating voltage of the bus bar after the phase change boosting of the target direct-drive fan;
the first-order hysteresis device is used for carrying out low-pass filtering on the effective value of the three-phase alternating voltage of the bus bar;
the comparator is used for outputting the penetration higher level signal when the effective value of the three-phase alternating voltage of the bus bar is lower than a preset low voltage penetration threshold value.
For example, as shown in fig. 4, the three-phase ac voltages WF1Vtr1SecA, WF1Vtr1SecB, WF1Vtr1SecC of the bus bar after the blower is boosted by the box transformer are detected on line in real time, the effective value of the three-phase voltage of the bus bar is calculated as WTPCC, the per-unit value WTPCCpu of the bus bar voltage is obtained after normalization and low-pass filtering, and is compared with 0.9pu, when the grid voltage drops by 10% or more, a high-level signal LVRT _ Det is output, and the direct-drive blower triggers low-voltage ride-through.
In some embodiments, the step of controlling, by the reactive power control module during the low voltage period of the grid-side control system, the target direct-drive wind turbine to output reactive power to the target power grid according to the voltage sag depth to support the power grid includes:
and the reactive power control module of the network side control system in the low voltage period calculates the reactive current corresponding to the reactive power according to the voltage drop depth by the following formula:
i ds_ref ＝1.5×(0.9-U pcc_pu )×1.1
in the formula i ds_ref Is a reactive current, 0.9-U pcc_pu To the voltage sag amplitude, U pcc_pu The effective value of the three-phase alternating voltage of the bus is obtained;
and controlling the target direct-drive fan to output the reactive current to the target power grid so as to support the power grid.
Illustratively, after triggering the low voltage ride through, the direct drive fan grid-side converter control system adjusts the reactive current command value according to i ds_ref ＝1.5×(0.9-U pcc_pu ) X 1.1, reactive power is emitted and the reactive control module during low voltage is as shown in fig. 5. And preferentially sending out reactive power, limiting the active power output, and the reference value of the active current of the inner ring of the network side converter is according to
Figure BDA0003652370960000091
Clipping is performed.
In some embodiments, the above method further comprises:
the low voltage ride through trigger module generates a low level recovery signal to activate a voltage recovery mode when detecting that the current voltage value of the target power grid is recovered to be greater than or equal to the preset reference value, wherein in the voltage recovery mode, a reactive power control module of the grid-side control system works in a normal voltage period and the reactive power control module is closed in a low voltage period, and a power control module works in a power control module and the active power control module is closed in a low voltage ride through period when the voltage of the machine-side control system is recovered;
the reactive power control module controls the target direct-drive fan to preferentially output active power to the target power grid during the voltage normal period of the grid-side control system;
and when the voltage of the machine side control system is recovered, the power control module controls the output power of the target direct-drive fan to be increased to a rated value according to the fixed increasing speed.
Illustratively, when a power grid fault disappears, the low voltage ride through trigger module detects that the power grid voltage recovers, a falling edge low level signal is generated, the fan enters an active power recovery stage and preferentially sends out active power, the active power control module during the low voltage ride through period of the direct-drive fan side converter control system is switched to the active power control module during the voltage recovery, the active current instruction Iqr _ ref value of the side converter is increased according to a fixed slope, and the side output power of the fan is gradually recovered to a rated value. If the control logic of the machine side converter control system is that after the low voltage of the power grid drops, an inner ring active current instruction value of the machine side converter in the low-penetration period is obtained through calculation according to the voltage drop amplitude of the grid side, and therefore the output active power of the machine side converter is limited in the low-penetration period. When the voltage of the power grid is recovered, the active current instruction value of the machine side converter is recovered according to a preset fixed slope, so that the active power output by the machine side converter is controlled to be gradually recovered.
In some embodiments, the above method further comprises:
under the condition that the current voltage value is recovered to be greater than or equal to the preset reference value, the target direct-drive fan controls power according to the following formula:
T e ＝1.5pΨ f i q
in the formula: t is a unit of e Representing the number of pole pairs and psi for the electromagnetic torque p of the direct-drive fan f Is a direct-drive fan rotor flux linkage i q Is the component of the direct drive fan stator current on the q axis.
Illustratively, when the voltage of the power grid is normal, the direct-drive fan machine side and grid side converters adopt an active control module during the voltage normal period and a reactive control module during the voltage normal period, namely, double closed-loop vector typical control. And the outer ring of the grid-side converter is subjected to constant reactive power control and constant direct current voltage control, so that the constant direct current voltage is ensured, and the unit power factor outputs the maximum active power to the power grid. Outer ring of machine side converter adopting Maximum Power Point Tracking (MPPT) control and i d The control is carried out as 0, wind energy output active power is captured according to MPPT, and stator current i is controlled q Controlling electromagnetic torque, i.e. T, of direct-drive fans e ＝1.5pΨ f i q In the formula: t is e For the direct-drive fan electromagnetic torque, p represents the pole pair number psi f For directly driving the rotor flux linkage i of the fan q Is the component of the direct drive fan stator current on the q axis. As can be seen, the electromagnetic torque of the direct-drive fan is driven by the active current i of the machine side converter q Determining and further controlling the output active power P of the converter at the machine side r . When the power grid fails, the grid-side converter outputs power P s The power of the machine side and the power of the network side are unbalanced when the direct current voltage is not sent out, namely, the direct current capacitor bears unbalanced energy caused by active unbalance of the two sides, and when the direct current voltage is larger than 1.4pu, the Chopper controls the unloading circuit to add hardware to release the energy. The direct-drive wind turbine generator side converter limits the output active power of the generator side converter in a low-voltage period, reduces the unbalanced energy of the generator side and the grid side, improves the stability of direct-current voltage, and simultaneously generates reactive power through the grid side converter to support the voltage of a power grid, so that the direct-drive wind turbine generator can realize low-voltage ride through more safely and reliably.
In some embodiments, the active control module during the low voltage ride through includes an adder and a limiter;
the adder is used for calculating the difference value between the target power grid voltage and a preset reference value;
the limiter is used to limit the adder output value within an acceptable range.
For example, as shown in fig. 6, the adder is used to calculate the difference between the grid voltage and the adjustment constant; the amplitude limiter is used for limiting the output of the adder to be between 0 and 1, ensuring that the machine side active power is larger than or equal to 0 during the low-voltage ride-through period, and obtaining an active current instruction Ir _ IqLVRT _0 during the low-voltage ride-through period after amplitude limiting.
In some embodiments, the voltage recovery power control module comprises a sample holder, an or gate, a first adder, a divider, a pulse generator, a not gate, an integrator, and a second adder;
the sampling holder is used for locking an active current value of an inner ring of the machine side converter entering low penetration when the voltage of a target power grid is not recovered to a preset reference value or the active power output by the fan side is not recovered to a rated value;
the first adder is used for calculating a difference value between an active current instruction value in a low voltage ride through mode and an active current value of an inner ring of the fan-side converter;
under the voltage recovery mode, the pulse generator receives and recovers a low level signal through an input end and sends out a high level signal with the time length being the output value of the divider through an output end;
the NOT gate is used for keeping a low-level signal in the voltage recovery mode;
the integrator is used for integrating according to a fixed slope value and outputting an inner loop active current instruction change value in a voltage recovery period;
the second adder is used for summing the inner-loop active current instruction change value output by the integrator and the active current instruction value in the low-voltage ride-through mode to obtain the active current instruction in the voltage recovery mode.
Illustratively, as shown in fig. 7, the power control module for voltage recovery includes a sample holder, an or gate, a first adder, a divider, a pulse generator, a not gate, an integrator, and a second adder. The sampling holder is used for locking the active current value of an inner ring of the machine side converter entering low penetration when the voltage of a power grid is not recovered to 0.9pu or the machine side output active power is not recovered; the first adder is used for calculating a difference value between the low-penetration active current instruction value and the active current value of the inner ring of the machine side converter entering low penetration, the output of the first adder is divided by a fixed slope value through a divider, and the recovery time value of the active current when the inner ring of the machine side converter is gradually increased to the active current entering low penetration is obtained; when the pulse generator is used for restoring a power grid, the input end receives a falling edge signal of which the high level is changed into the low level, and the output end sends out a high level signal of which the time length is the output value of the divider; the input end of the NOT gate is output by a pulse generator, and 0 is output after a high level signal in the low-penetration recovery process is negated; the NOT gate is used for keeping a low level signal during a low-pass recovery period, the integrator performs integration according to a fixed slope value and outputs an inner loop active current instruction change value during a voltage recovery period; and the second adder is used for summing the change value of the inner-loop active current instruction output by the integrator and the active current instruction value in the low-pass period to obtain the active current instruction Iqr _ ref in the voltage recovery period.
In some examples, the direct-drive fan side converter control system triggers low-pass active control during a low voltage period, the active control module during the low voltage pass active control module is as shown in fig. 6, and when the bus bar voltage per unit value WTPCCpu is lower than 0.2, the active current command is 0. And after the voltage difference value passes through the limiting amplitude value, obtaining an active current instruction Ir _ IqLVRT _0 value in the low-penetration period.
With the disappearance of the power grid fault, the power grid voltage starts to recover, and the active control module is shown in fig. 7 when the voltage of the direct-drive fan machine side converter control system recovers. As long as the grid voltage does not return to 0.9pu or the active current does not return to the lock value at the time of low pass, the low-voltage trigger signal LVRT _ Det and the recovery trigger signal LVRT _ Rcov output high-level signals after passing through the or gate, so as to keep locking the active current value WT1IqSTPURef0 just entering the time of low pass. And obtaining a difference value between the current command value and the current command value Ir _ IqLVRT _0 for limiting the active power in the low-penetration period, and dividing the difference value by a preset active current fixed slope recovery value LV _ Rate to obtain the time for recovering to the active current value WT1IqSTPURef0 at the low-penetration moment. Along with the gradual recovery of the voltage, when the voltage is more than 0.9pu, the input end of the pulse generator receives a falling edge signal of which the high level is changed into the low level, and the output end of the pulse generator sends out a high level signal of which the time length is the output value of the divider. And in the active current instruction recovery time, the integrator always integrates according to a preset fixed slope value, an inner ring active current instruction recovery value in a voltage recovery period is output, and then the value is summed with an active current instruction value Ir _ IqLVRT _0 in a low penetration period to obtain an active current instruction Iqr _ ref in the voltage recovery period, so that the wind turbine generator is controlled to output active power which is gradually recovered to a value before low penetration according to the fixed slope.
When the voltage of the power grid is normal, the direct-drive fan grid-side converter adopts a reactive power control module in the voltage normal period, namely, constant control with reactive power equal to 0 is adopted. With the normal voltage of a power grid and the recovery of the active power of the direct-drive fan to a rated state, the active power control of the machine side converter adopts an active power control module in the normal voltage period, namely, the active power output by wind energy is captured according to the maximum power tracking.
In the simulation experiment process, the direct-drive fan low-voltage ride-through control method and system are constructed through RTDS real-time simulation and are applied to a full electromagnetic transient simulation system with a direct-drive wind power plant connected with an infinite power supply. Setting a low-voltage fault on a power grid side, dropping the voltage of the power grid side to 20%, cutting off the fault after the voltage lasts for 625ms, obtaining simulation waveforms of an active power per unit value WFPPU, a reactive power per unit value WFQPU and a bus bar voltage per unit value WTPPCCpu of the wind turbine generator as shown in fig. 8, providing reactive support for the power grid when the voltage drops to 20%, and recovering the active power to the value before the fault at the power change rate of 500% Pn/s after low-voltage penetration.
The result obtained by the method is compared with the simulation result of the traditional control (only controlling the grid-side converter), the direct-current voltage comparison result is shown in a graph 9 and a graph 10, the direct-current voltage under the traditional control has the oscillation problem, the direct-current voltage under the control of the method is as low as 0.8pu during the low-voltage penetration period, and the direct-current voltage rapidly rises to 1.3pu at the voltage recovery moment and then gradually recovers the stable state. Comparing the current comparison results of the dq axis inner loop of the machine side converter in the figures 11 and 12, the active current under the control of the invention is limited to 0 in low-pass, and the dq axis current under the control of the traditional method continuously oscillates in the low-pass period.
Referring to fig. 13, the present invention further provides a direct drive fan low voltage ride through control device, including:
the detection unit 21 is configured to generate a ride-through high level signal to activate a low voltage ride-through mode when detecting that a current voltage value of a target power grid where a target direct-drive fan is located is lower than a preset reference value, where the direct-drive fan low voltage ride-through control system includes a grid-side control system and a machine side control system, in the low voltage ride-through mode, a reactive power control module of the grid-side control system is turned off during a normal voltage period and a reactive power control module of the machine side control system is operated during a low voltage period, and an active power control module of the machine side control system is turned off during a normal voltage period and an active power control module of the machine side control system is operated during a low voltage ride-through period;
a calculating unit 22, configured to calculate a voltage sag depth according to the current voltage value and the preset reference value;
the first control unit 23 is configured to control the target direct-drive fan to output reactive power to the target power grid according to the voltage drop depth so as to support the target power grid;
and the second control unit 24 is used for controlling the output power of the target direct-drive fan according to the voltage drop depth.
As shown in fig. 14, the embodiment of the present application further provides an electronic device 300, which includes a memory 310, a processor 320 and a computer program 311 stored on the memory 320 and executable on the processor, wherein when the computer program 311 is executed by the processor 320, the steps of any one of the above-mentioned methods for controlling the outlet temperature of the trough solar thermal field are implemented.
Since the electronic device described in this embodiment is a device used for implementing the outlet temperature control apparatus of the trough-type solar thermal collection field in this embodiment, based on the method described in this embodiment, a person skilled in the art can understand the specific implementation manner of the electronic device of this embodiment and various variations thereof, so that how to implement the method in this embodiment by the electronic device is not described in detail herein, and as long as the person skilled in the art implements the device used for implementing the method in this embodiment, the scope of protection intended by this application is included.
In a specific implementation, the computer program 311 may implement any of the embodiments corresponding to fig. 1 when executed by a processor.
It should be noted that, in the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to relevant descriptions of other embodiments for parts that are not described in detail in a certain embodiment.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The embodiment of the present application further provides a computer program product, where the computer program product includes computer software instructions, and when the computer software instructions are run on a processing device, the processing device is enabled to execute a flow of the direct drive fan low voltage ride through control method in the embodiment corresponding to fig. 1.
The computer program product includes one or more computer instructions. The procedures or functions according to the embodiments of the present application are all or partially generated when the computer program instructions are loaded and executed on a computer. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored on a computer readable storage medium or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. A computer-readable storage medium may be any available medium that a computer can store or a data storage device, such as a server, a data center, etc., that is integrated with one or more available media. The usable medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, a division of a unit is merely a logical division, and an actual implementation may have another division, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method of the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.

Claims (10)

1. A low voltage ride through control method of a direct drive fan is used for a low voltage ride through control system of the direct drive fan, and is characterized by comprising the following steps:
under the condition that a low voltage ride through trigger module detects that the current voltage value of a target power grid where a target direct-drive fan is located is lower than a preset reference value, generating a ride through high level signal to activate a low voltage ride through mode, wherein a direct-drive fan low voltage ride through control system comprises a grid side control system and a machine side control system, in the low voltage ride through mode, a reactive power control module of the grid side control system is closed in a voltage normal period and works in a low voltage period, and an active power control module of the machine side control system is closed in a voltage normal period and works in a low voltage ride through period;
calculating the voltage drop depth according to the current voltage value and the preset reference value;
a reactive power control module of the grid side control system during a low voltage period controls the target direct-drive fan to output reactive power to the target power grid according to the voltage drop depth so as to support the target power grid;
and an active control module of the machine side control system controls the output power of the target direct drive fan according to the voltage drop depth during the low voltage ride through period.
2. The method of claim 1, wherein the low voltage ride through trigger module comprises an effective value calculator, a first order hysteresis, and a comparator;
the effective value calculator is used for calculating the effective value of the three-phase alternating voltage of the bus bar after the phase change boosting of the target direct-drive fan;
the first-order hysteresis device is used for carrying out low-pass filtering on the bus bar three-phase alternating voltage effective value;
the comparator is used for outputting the ride-through high level signal when the bus bar three-phase alternating voltage effective value is lower than a preset low voltage ride-through threshold value.
3. The method of claim 1, wherein the step of the during-low-voltage reactive control module of the grid-side control system controlling the target direct drive wind turbine to output reactive power to the target grid to support the grid according to the voltage sag depth comprises:
and a reactive power control module of the network side control system in a low voltage period calculates reactive current corresponding to reactive power according to the voltage drop depth by the following formula:
i ds_ref ＝1.5×(0.9-U pcc_pu )×1.1
in the formula i ds_ref Is a reactive current, 0.9-U pcc_pu To the voltage sag amplitude, U pcc_pu The effective value of the three-phase alternating voltage of the bus is obtained;
and controlling the target direct-drive fan to output the reactive current to the target power grid so as to support the power grid.
4. The method of claim 1, further comprising:
the low voltage ride through triggering module generates a low level recovery signal to activate a voltage recovery mode when detecting that the current voltage value of the target power grid is recovered to be greater than or equal to the preset reference value, wherein in the voltage recovery mode, a reactive power control module of the grid side control system works in a normal voltage period and is closed in a low voltage period, and a power control module works in a power recovery period and is closed in a low voltage ride through period when the voltage of the machine side control system is recovered;
a reactive power control module of the grid side control system controls the target direct-drive fan to preferentially output active power to the target power grid during a normal voltage period;
when the voltage of the machine side control system is recovered, the power control module controls the output power of the target direct-drive fan to be increased to a rated value according to the fixed increasing speed.
5. The method of claim 4, further comprising:
under the condition that the current voltage value is recovered to be greater than or equal to the preset reference value, the target direct-drive fan controls power according to the following formula:
T e ＝1.5pΨ f i q
in the formula: t is a unit of e Representing the number of pole pairs and psi for the electromagnetic torque p of the direct-drive fan f For directly driving the rotor flux linkage i of the fan q Is the component of the direct drive fan stator current on the q axis.
6. The method of claim 1, wherein the active control module during the low voltage ride through comprises an adder and a limiter;
the adder is used for calculating the difference value between the target power grid voltage and a preset reference value;
the limiter is used for limiting the output value of the adder within an acceptable range.
7. The method of claim 1, wherein the voltage recovery power control module comprises a sample holder, an OR gate, a first adder, a divider, a pulse generator, a NOT gate, an integrator, and a second adder;
the sampling retainer is used for locking an active current value of an inner ring of the machine side converter entering low penetration when the voltage of a target power grid is not recovered to a preset reference value or the active power output by the fan side is not recovered to a rated value;
the first adder is used for calculating a difference value between an active current instruction value in a low voltage ride through mode and an active current value of an inner ring of the fan-side converter;
the pulse generator receives and recovers a low level signal through an input end and sends out a high level signal with the time length being the output value of the divider through an output end in the voltage recovery mode;
the NOT gate is used for keeping a low-level signal in the voltage recovery mode;
the integrator is used for integrating according to a fixed slope value and outputting an inner loop active current instruction change value in a voltage recovery period;
and the second adder is used for summing the inner-loop active current instruction change value output by the integrator and the active current instruction value in the low-voltage ride-through mode to obtain the active current instruction in the voltage recovery mode.
8. A kind of wind-driving machine low voltage ride through controlling device, characterized by that, comprising:
the detection unit is used for generating a ride-through high-level signal to activate a low-voltage ride-through mode under the condition that the current voltage value of a target power grid where a target direct-drive fan is located is detected to be lower than a preset reference value, wherein the direct-drive fan low-voltage ride-through control system comprises a grid-side control system and a machine-side control system, in the low-voltage ride-through mode, a reactive power control module of the grid-side control system is closed in a voltage normal period and works in a low-voltage period, and an active power control module of the machine-side control system is closed in a voltage normal period and works in a low-voltage ride-through period;
the calculating unit is used for calculating the voltage drop depth according to the current voltage value and the preset reference value;
the first control unit is used for controlling the target direct-drive fan to output reactive power to the target power grid according to the voltage drop depth so as to support the target power grid;
and the second control unit is used for controlling the output power of the target direct drive fan according to the voltage drop depth.
9. A direct drive fan low voltage ride through control system capable of realizing any one of the direct drive fan low voltage ride through control methods of claims 1-8, the direct drive fan low voltage ride through control system is characterized by comprising: the device comprises a low voltage ride through triggering module, a reactive power control module in a voltage normal period, a reactive power control module in a low voltage period, an active power control module in a voltage normal period, an active power control module in a low voltage ride through period and an active power control module in voltage recovery.
10. A direct drive wind turbine comprising the direct drive wind turbine low voltage ride through control system of claim 9.
CN202210545507.XA 2022-05-18 2022-05-19 Low voltage ride through control method for direct-drive fan and related equipment Pending CN115085250A (en)

Applications Claiming Priority (2)

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CN2022105388465 2022-05-18
CN202210538846 2022-05-18

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Country Link
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