CN108879759B - Harmonic analysis and treatment method for grid connection of double-fed wind generating set - Google Patents
Harmonic analysis and treatment method for grid connection of double-fed wind generating set Download PDFInfo
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Abstract
The invention discloses a harmonic analysis and treatment method for grid connection of a doubly-fed wind generating set, which is characterized in that an electromagnetic transient model of the doubly-fed wind generating set is constructed based on a mathematical model of the doubly-fed wind generating set; performing electromagnetic transient simulation calculation on the wind power plant by using an ADPSS simulation system to obtain harmonic current and harmonic voltage injected into a power grid by the wind power plant; comparing the obtained harmonic current and harmonic voltage of the wind power plant input power grid with limit values respectively, and judging whether the harmonic current or the harmonic voltage of the wind power plant input power grid exceeds the standard or not; and if the harmonic current input into the power grid by the wind power plant exceeds the standard, designing an active filter, establishing a wind power plant electromagnetic transient model containing the active filter, and compensating the harmonic current in the power grid. The invention has important guiding significance for evaluating the harmonic influence generated by accessing a large-scale wind power plant in the Mongolian region to a power grid based on the wind power plant simulation calculation and harmonic analysis of the ADPSS and a filter electromagnetic transient model designed aiming at the condition that the harmonic exceeds the standard.
Description
Technical Field
The invention relates to the technical field of power grid power quality evaluation research, in particular to a harmonic analysis and treatment method for grid connection of a double-fed wind generating set.
Background
The inner Mongolia autonomous region is wide in region and rich in resources, and is an important energy, heavy chemical industry, metallurgy, building material and other raw material production and output base in China. Due to the unique characteristics of energy resource endowment and economic and social development, the autonomous region is in the rapid development period of large-scale resource development and processing conversion, the heavy industrial structure mainly comprising new energy resources such as wind power and photovoltaic in Mongolia in a short period is difficult to change fundamentally, and in addition, the rapid development of the new energy resources such as the wind power and the photovoltaic makes the new energy resources such as the wind power and the photovoltaic become the typical nonlinear harmonic source of Mongolian power grid.
A wind power generation system is an energy conversion system that converts wind energy into electrical energy. As a renewable energy source, the development and utilization of wind energy have attracted great attention in recent years, and a large number of wind power generation systems have been put into operation, and various wind power generation technologies have become mature day by day. The Mongolian region is used as one of eight million kilowatt-level wind power bases planned by the state, and the technical development amount of regional wind energy resources is about 1.1 hundred million kilowatts. In 2015, the wind power generation amount in the Mondon power supply region is accumulated to 30.16 hundred million kilowatt hours and is increased by 2.1 percent on the same scale. By 2015, the installed wind power capacity in the Mongolian area reaches 815 ten thousand kilowatts, the installed wind power capacity is increased by 8.6 percent on the same scale, and the installed wind power capacity accounts for 33 percent of the total installed capacity of the area.
Mongolian electric power highly attaches importance to the development of clean energy, continuously and deeply digs potential on conventional measures such as accelerating the promotion of power grid construction, strengthening electric power demand side management, strengthening heat supply unit operation management, fully digging system peak regulation potential and the like, and promotes a series of innovative measures to promote local wind power consumption.
In the power supply range of the Mongolian power grid, the power grid structure is relatively weak. With the rapid construction of an extra-high voltage alternating current-direct current hybrid power grid, a large amount of new energy (wind power, photovoltaic and the like) is connected to the grid, so that the problem of the electric energy quality of the Mongolian power grid is increasingly highlighted, and therefore the Mongolian power grid takes the development of new service energy as important political and social responsibility and actively supports the development of the wind power industry. In recent years, new wind power energy power generation in Mongolian areas develops rapidly, a large number of wind power plants are connected into a power grid to operate, and the Mongolian power grid becomes a provincial power grid which has the highest wind power consumption level and the fastest development in China at present. Meanwhile, due to the dynamic fluctuation change of wind speed of the wind power plant, the output power of the new energy grid-connected power generation has large random fluctuation, and the intermittent power fluctuation can cause adverse effect on the electric energy quality of the power grid. Generally, most of new energy power generation systems are connected to the grid by adopting power electronic devices, voltage and current harmonics generated by the power electronic devices are inevitable, even negative sequence voltage generated by asymmetric faults of a power grid and voltage harmonics of the power grid interact with a converter of a new energy power station, the converter generates additional harmonic current, and the new energy is connected to the power grid, so that the power quality of the power grid is greatly influenced. Therefore, how to analyze the influence of the wind power plant grid connection on the power quality of a power grid and determine the distribution conditions of harmonic voltage and harmonic current in the system still remains a technical problem to be solved.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a harmonic analysis and treatment method for grid connection of a double-fed wind generating set.
The technical scheme adopted by the invention is as follows:
a harmonic wave analysis and treatment method for grid connection of a double-fed wind generating set comprises the following steps:
the method comprises the following steps: constructing an electromagnetic transient model of the doubly-fed wind generating set based on the mathematical model of the doubly-fed wind generating set;
step two: performing electromagnetic transient simulation calculation on the wind power plant by using an ADPSS simulation system to obtain harmonic current and harmonic voltage injected into a power grid by the wind power plant;
step three: comparing the obtained harmonic current and harmonic voltage of the wind power plant input power grid with limit values respectively, and judging whether the harmonic current or the harmonic voltage of the wind power plant input power grid exceeds the standard or not;
step four: and if the harmonic current input into the power grid of the wind power plant exceeds the standard, designing an active filter, establishing a wind power plant electromagnetic transient model containing the active filter, and verifying the treatment effect of the harmonic current.
Further, the mathematical model of the doubly-fed wind turbine generator is as follows:
wherein, the stator and rotor flux linkage is expressed as:
the electromagnetic torque and the rotor motion equation of the generator are as follows:
TJps＝Tm-Te
in the formula, p represents a differential operator; subscripts s and r denote the stator and rotor of the machine, Ls、Lr、LmThe self inductance of the stator and the rotor and the mutual inductance between the stator and the rotor are respectively; subscripts d, q represent the quantities on the d-axis and q-axis, respectively, in dq0 coordinates; u, i,
R represents voltage, current, flux linkage and resistance, respectively; omega is the angular speed of the rotor; s is slip; t iseIs an electromagnetic torque; t ismIs the generator mechanical torque; t isJIs the rotor inertia time constant.
Further, the electromagnetic transient model of the double-fed wind generating set comprises a generator converter model, a wind power transmission shaft control model, a pitch angle control model and an electrical control model;
the generator and converter model comprises an active control channel and a reactive control channel, wherein the active control channel takes an excitation voltage control signal obtained by calculation of the electrical control model as an input signal and outputs an active current signal; the reactive control channel takes an active current control signal obtained by calculation of the electrical control model as an input signal and outputs a reactive current signal;
the wind power transmission shaft control model comprises an impeller rotational inertia part and a generator rotational inertia part, the impeller and the generator are connected through a spring, the pneumatic power from the impeller and the electromagnetic power from the generator are used as two inputs, and the speed deviation of the impeller and the generator rotor is obtained under the regulation of a pitch angle; the pitch angle control model comprises a front half part and a rear half part, wherein the front half part is controlled by the rotating speed omega of the generatorgAs an input signal, a pitch control signal is given through a PI control link, and the power P of the generator is usedordThe back half takes the sum of the pitch control signal and the pitch compensation signal as input, and outputs a pitch angle β through a PI control integration link;
in the pitch angle control model, when power P transmitted to the generatorordGreater than PMXOr generator speed omegagWhen the rotating speed is greater than the rotating speed reference value, the wind generating set increases the pitch angle in a fast pitch changing mode so as to reduce the rotating speed of the generator;
the electric control model comprises a WPMS model, an excitation controller and a power factor controller, wherein the WPMS model simulates voltage reactive power control of a wind power plant, the excitation controller simulates a converter/excitation system, and the power factor controller monitors the power factor of a fan grid-connected point.
Further, the method for calculating the harmonic current of the wind power plant input power grid comprises the following steps:
calculating a harmonic current limit value allowed to be injected into a power grid after the wind power plant is accessed;
according to the established electromagnetic transient model of the double-fed wind generating set, carrying out simulation calculation by adopting an ADPSS simulation platform to obtain a current waveform flowing to a grid-connected point by a wind power plant on a line;
carrying out discrete Fourier transform on the current waveform obtained by simulation to obtain a harmonic current value injected into a power grid by the wind power plant;
and comparing the harmonic current value injected into the power grid by the wind power plant with the harmonic current limit value, if the harmonic current value is smaller than the harmonic current limit value, the harmonic current value is qualified, and otherwise, the harmonic current value is considered as exceeding the standard.
Further, the method for calculating the harmonic voltage of the wind power plant input power grid comprises the following steps:
according to the power quality-public power grid harmonic regulation standard, calculating the power grid subharmonic voltage content and the voltage total harmonic distortion rate generated at a grid-connected point by the harmonic current injected into the power grid by the wind power plant; wherein:
the content rate of each harmonic voltage of the power grid is as follows:
in the formula of UNIs the nominal voltage of the grid; skThree-phase short circuit capacity of a common connection point; i ishIs the h harmonic current;
the total harmonic distortion rate of the voltage is:
in the formula, HRUhThe voltage content of the h-th harmonic is shown.
Comparing the content of each harmonic voltage of the power grid caused by the harmonic current injected into the power grid by the wind power plant at the common point with the content limit value of each harmonic voltage of the power grid, if the former is smaller than the latter, the qualification is represented, otherwise, the standard exceeding is regarded;
and comparing the total voltage harmonic distortion rate caused by the harmonic voltage of the wind power plant input power grid at the common point with the total voltage harmonic distortion rate limit value, if the former is smaller than the latter, the result is qualified, and otherwise, the result is regarded as exceeding the standard.
Further, the method for designing the active filter and establishing the wind power plant electromagnetic transient model containing the active filter comprises the following steps:
filtering out harmonic current of the exceeding times generated by the wind turbine generator, designing an active filter based on the harmonic current generated by the wind turbine generator, additionally installing the filter on the booster station side of the wind farm, and establishing an electromagnetic transient model of the wind farm additionally provided with the active filter.
Compared with the prior art, the invention has the beneficial effects that:
(1) the electromagnetic transient model of the doubly-fed wind generating set is established based on the mathematical model of the variable-speed variable-pitch doubly-fed wind generating set, the wind power plant simulation calculation and harmonic analysis based on the ADPSS and the filter electromagnetic transient model designed aiming at the condition that the harmonic exceeds the standard have important guiding significance for evaluating the harmonic influence generated by the large-scale wind power plant connected to a power grid in the Mongolian region;
(2) according to the invention, the harmonic current generated by the wind power plant is suppressed by establishing the electromagnetic transient model of the active filter, so that harmonic voltage distortion caused by a harmonic source at a public connection point is eliminated or reduced, and the power quality is improved.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a flow chart of a harmonic wave analysis and treatment method for grid connection of a double-fed wind generating set;
FIG. 2 is an overall block diagram of an electromagnetic transient model of the doubly-fed wind turbine generator system;
FIG. 3 is a generator converter model control block diagram;
FIG. 4 is a block diagram of a wind drive shaft control model;
FIG. 5 is a pitch angle control model block diagram;
FIG. 6 is a block diagram of an electrical control model;
FIG. 7 is a schematic diagram of a wind farm electromagnetic transient model without a filter;
FIG. 8 is a schematic current waveform of a UK sleeve sea wind farm common junction (PCC);
FIG. 9 is a schematic diagram of a wind farm electromagnetic transient model with a filter added.
Detailed Description
The invention is further described with reference to the following figures and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As introduced in the background art, the research on systematic analysis and verification of modeling, simulation, evaluation and management is less in the prior art aiming at the harmonic influence of the wind driven generator set on the power grid, and the research on systematic modeling, simulation, evaluation and management verification is carried out for mastering the harmonic influence of the doubly-fed wind driven generator set on the power grid in the eastern Mongolia.
As shown in fig. 1, an embodiment of the present invention provides a harmonic analysis and treatment method for grid connection of a doubly-fed wind turbine generator system, including the following steps:
the method comprises the following steps: and constructing an electromagnetic transient model of the doubly-fed wind generating set based on the mathematical model of the doubly-fed wind generating set.
The mathematical model of the double-fed wind turbine generator is as follows:
wherein, the stator and rotor flux linkage is expressed as:
the electromagnetic torque and the rotor motion equation of the generator are as follows:
TJps＝Tm-Te
in the formula, p represents a differential operator; subscripts s and r denote the stator and rotor of the machine, Ls、Lr、LmThe self inductance of the stator and the rotor and the mutual inductance between the stator and the rotor are respectively; subscripts d, q represent the quantities on the d-axis and q-axis, respectively, in dq0 coordinates; u, i,
R represents voltage, current, flux linkage and resistance, respectively; omega is the angular speed of the rotor; s is slip; t iseIs an electromagnetic torque; t ismIs the generator mechanical torque; t isJIs the rotor inertia time constant.
The electromagnetic transient modeling of the double-fed wind generating set by adopting the ADPSS platform comprises the following steps: the method comprises the following steps of engineering data entry, network division, task allocation and submission, calculation execution and result output. Electromagnetic transient modeling adopts a graphic mode to create a system model circuit diagram and a control system diagram, and a dialog box mode is used for inputting parameters. The elements can be displayed by a single line diagram or a multi-line diagram; the element display style may be customized by a user. The circuit diagram can be displayed in a layered mode and has a structure of 'multilayer nesting', and the structure is clear.
As shown in fig. 2, the electromagnetic transient model of the doubly-fed wind turbine generator system includes a generator converter model, a wind power transmission shaft control model, a pitch angle control model and an electrical control model; wherein the content of the first and second substances,
as shown in fig. 3, the generator converter model includes an active control channel and a reactive control channel, and the active control channel takes an active current control signal calculated by the electrical control model as an input signal and outputs an active signal; and the reactive control channel takes an excitation voltage control signal obtained by calculation of the electrical control model as an input signal and outputs a reactive signal.
As shown in fig. 4, the wind power transmission shaft control model comprises an impeller rotational inertia part and a generator rotational inertia part, the impeller and the generator are connected through a spring, the pneumatic power from the impeller and the electromagnetic power from the generator are used as two inputs, and under the adjustment of a pitch angle, the speed deviation of the impeller and the generator rotor is obtained.
As shown in fig. 5, the pitch angle control model includes a front half and a rear half, and the front half is controlled by the generator speed ωgAs an input signal, a pitch control signal is given through a PI control link, and the power P of the generator is usedordThe back half takes the sum of the pitch control signal and the pitch compensation signal as input, and outputs the pitch angle β through a PI control integration link.
In the pitch angle control model, when power P transmitted to the generatorordGreater than PMXOr generator speed omegagAnd when the pitch angle is larger than the rotating speed reference value, the wind generating set increases the pitch angle in a fast pitch changing mode so as to reduce the rotating speed of the generator.
As shown in fig. 6, the electrical control model includes a WPMS model, an excitation controller and a power factor control, wherein the WPMS model simulates voltage reactive power control of a wind farm, the excitation controller simulates a converter/excitation system, and the power factor control monitors a power factor of a wind turbine grid-connected point.
Step two: electromagnetic transient simulation calculation is carried out on the wind power plant by using the ADPSS simulation system, and harmonic current injected into a power grid by the wind power plant and generated harmonic voltage are obtained.
The method for calculating the harmonic current injected into the power grid by the wind power plant comprises the following steps:
according to the national standard GB/T14549-93 electric energy quality public power grid harmonic wave, on the distribution principle of harmonic current at a PCC (point of common coupling), distributing the allowable value of the harmonic current injected into the power grid by each user at the same point of common coupling according to the ratio of the protocol capacity of the user at the point of common coupling to the capacity of the power supply equipment at the point of common coupling, and calculating the limit value of the harmonic current allowed to be injected into the power grid after the wind power plant is accessed;
calculating by adopting an ADPSS simulation platform according to the established electromagnetic transient model of the doubly-fed wind generating set to obtain a current waveform flowing to a grid-connected point of a wind power plant on a line;
carrying out Discrete Fourier Transform (DFT) transformation on the current waveform obtained by simulation to obtain a harmonic current value injected into a power grid by the wind power plant; for a sequence of N points, its Discrete Fourier Transform (DFT) is
The calculation method for generating the harmonic voltage after the wind power plant is connected to the power grid comprises the following steps:
according to the national standard GB/T14549-1993 electric energy quality-public power grid harmonic wave, the content of each harmonic voltage of a power grid generated at a grid-connected point by harmonic current injected into the power grid of a wind power plant is calculated as follows:
in the formula of UNIs the nominal voltage of the grid; skThree-phase short circuit capacity of a common connection point; i ishIs the h harmonic current.
The total harmonic distortion rate of the voltage is:
step three: comparing the obtained harmonic current and harmonic voltage with limit values respectively, and judging whether the harmonic current or the harmonic voltage of the wind power plant input power grid exceeds the standard or not;
the step of comparing the resulting harmonic current with a limit value comprises:
and comparing the harmonic current value injected into the power grid by the wind power plant with the harmonic current limit value, if the harmonic current value is smaller than the harmonic current limit value, the harmonic current value is qualified, and otherwise, the harmonic current value is considered as exceeding the standard.
The step of comparing the resulting harmonic voltage with a limit value comprises:
comparing the content of each harmonic voltage of the power grid generated by harmonic current injected into the power grid at the grid-connected point of the wind power plant with the limit value of each harmonic voltage, if the former is smaller than the latter, the power grid is qualified, otherwise, the power grid is considered as exceeding the standard;
comparing the total harmonic distortion rate of the voltage caused by the harmonic voltage of the wind power plant input power grid at the common point with the total harmonic distortion rate limit value of the voltage, if the total harmonic distortion rate of the voltage is smaller than the total harmonic distortion rate limit value of the voltage, the voltage is qualified, otherwise, the voltage is considered as exceeding the standard.
Step four: and if the harmonic current input into the power grid of the wind power plant exceeds the standard, designing an active filter, establishing a wind power plant electromagnetic transient model containing the active filter, and verifying the treatment effect of the harmonic current.
Filtering out harmonic current of the exceeding times generated by the wind turbine generator, designing an active filter based on the harmonic current generated by the wind turbine generator, additionally installing the filter on the booster station side of the wind farm, establishing a wind farm electromagnetic transient model additionally provided with the active filter, carrying out simulation calculation again to obtain the harmonic current of the wind farm injected into a power grid after the filter is additionally installed, comparing the harmonic current of the wind farm injected into the power grid before and after the filter is additionally installed, and verifying the effectiveness of the wind farm electromagnetic transient model additionally provided with the active filter.
The existing research aiming at the harmonic influence of a wind power generator set on a power grid is less in systematic analysis and verification for comprehensively carrying out modeling, simulation, evaluation and treatment. The harmonic analysis and treatment method for grid connection of the double-fed wind generating set establishes an electromagnetic transient model of the double-fed wind generating set based on a variable speed variable pitch double-fed wind generating set mathematical model, and has important guiding significance for evaluating harmonic influence generated by accessing a large-scale wind power plant to a power grid in Mongolian regions based on wind power plant simulation calculation and harmonic analysis of an ADPSS and a filter electromagnetic transient model designed aiming at the condition that harmonic exceeds standard.
In order to make the present invention better understood by those skilled in the art, a specific embodiment is illustrated below, wherein a model analysis is performed by taking an inner Mongolian electric jacket sea wind farm as an example, and the Mongolian electric jacket sea wind farm planning deviceThe machine capacity is 350MW, the construction is divided into two stages, the installed capacity of the first stage is 49.5MW, the second stage is at the south side of the first stage site, and the installed capacity is 300 MW. The second-stage engineering floor area of the inner Mongolia Hua-Dy-Ke-Wu-Tu-sleeve sea wind electric field is 98km3And 200 1500kW wind generating sets are installed, and the installed capacity is 300 MW.
The electromagnetic transient model built in the ADPSS program is shown in fig. 7.
1. Harmonic calculation analysis
(1) Harmonic current calculation and conclusions
234 double-fed asynchronous machines of 1500kW are selected for the wind power plant, and the system is accessed in a 220kV voltage class.
Short circuit capacity of Sk1The allowable value of the h harmonic current is as follows:
in the formula, Sk1Minimum short circuit capacity for the point of common connection; sk2As a reference short circuit capacity; i ishpIs the h-th harmonic current allowable value according to the regulation of GB/T14549-93 harmonic of electric energy quality public power grid, A; i ishTo short circuit capacity of Sk1The allowable value of the h harmonic current.
According to the national standard GB/T14549-1993 "power quality-utility grid harmonics" concerning the distribution principle of harmonic currents at a point of common coupling PCC, the allowable value of the harmonic current injected into the grid by each user of the same point of common coupling is distributed as the ratio of the protocol capacity of this user at this point to the power supply equipment capacity of its point of common coupling. The h-th harmonic current allowable value of the ith user at the common connection point is as follows:
wherein S isiThe power utilization protocol capacity of the ith user; stCapacity of power supply equipment for point of common connection α is phase superposition coefficient, Si350MVA (second-phase wind power generation capacity), St＝1524MVA。
According to the established electromagnetic transient model of the wind power plant, the electromagnetic transient model is combined with the actual wind power plant of the Wu Chi wind, harmonic analysis simulation calculation is carried out by using an ADPSS program, and the current waveform of a public connection Point (PCC) of the Wu Chi wind power plant is obtained and is shown in figure 8.
And performing DFT conversion on the time domain waveform obtained by simulation to obtain the harmonic current value of the input power grid of the Wu Ching sea wind farm. And calculating a harmonic current limit value which allows the UK sea wind power plant to be injected into the common point according to national standards, comparing the harmonic current value which is calculated according to the electromagnetic transient model of the wind power plant and is output by the wind power plant with the limit value, if the harmonic current value is smaller than the limit value, the harmonic current value is qualified, otherwise, the harmonic current value is considered as exceeding the standard, and the specific comparison result is shown in table 1.
TABLE 1 comparison of injected harmonic current at 220kV common point with the limit
According to the calculation result, the harmonic currents injected into the common point of the wind power plant calculated at this time are larger by 3, 5 and 7 times and exceed the harmonic current limit value, and a corresponding filter needs to be installed.
(2) Harmonic voltage calculation and conclusions
The content rate of each harmonic voltage of the power grid is as follows:
in the formula of UNIs the nominal voltage, U, of the power gridN＝220kV；SkThree-phase short-circuit capacity, S, for common connection pointsk＝1987MVA；IhIs the h harmonic current.
The total harmonic distortion rate of the voltage is:
in the formula, HRUhThe voltage content of the h-th harmonic is shown.
And comparing the power grid harmonic content and the voltage total harmonic distortion caused by the harmonic current output by the wind power plant at the common point with the national standard 220kV public power grid harmonic voltage content and the voltage total harmonic distortion limit, if the power grid harmonic content and the voltage total harmonic distortion limit are smaller than the limit, the power grid harmonic content and the voltage total harmonic distortion are qualified, otherwise, the power grid harmonic content and the voltage total harmonic distortion are considered to be over-standard, and specific comparison results are shown in a table 2.
TABLE 2 comparison of injection of harmonic voltage at 220kV common and limiting
The comparison result of the total harmonic distortion rate of the voltage caused by the harmonic current of the power grid injected by the wind power plant at the public point and the total harmonic distortion rate limit value of the voltage of the 220kV public power grid specified by the national standard is shown in the following table:
TABLE 3 comparison of the total harmonic distortion of the wind farm at PCC points with the limit
According to the calculation result, the content of each harmonic voltage of the power grid caused by the Wuqi sea wind farm at the common point is qualified and does not exceed the standard; the total harmonic distortion of 220kV voltage is qualified, and the national standard requirement is met.
2. Wind farm harmonic treatment
(1) Wind farm filter design and model thereof
The Wu-Chi sea wind farm has certain harmonic components at the common connection point, the larger harmonic components are 3, 5 and 7, and the maximum harmonic current is 3 harmonic waves. When the power grid is connected, the buses of all levels have certain voltage distortion but are within an allowable range.
The 3 rd harmonic current, the 5 th harmonic current and the 7 th harmonic current injected into a public connection point (a poplar ditch gate station and a 220kV bus) by the Wu Shui Hai electric field are larger and exceed the allowable value, wherein the 3 rd harmonic current is the largest. According to the requirement, an active filter aiming at filtering 3, 5 and 7 harmonic currents is designed and additionally arranged on the 35kV side of the wind power plant booster station, and a wind power plant electromagnetic transient model additionally provided with the active filter is established, as shown in fig. 9, wherein the active filter is arranged in a red frame. The wind power plant electromagnetic transient model with the active filter is used for compensating harmonic current generated by the wind power plant to eliminate or reduce harmonic current injection of a harmonic source to a public connection point and harmonic voltage distortion caused by the harmonic current injection, so that the power quality is improved.
(2) Harmonic analysis with filter
And after an active filter is additionally arranged, carrying out harmonic analysis calculation on the Wuqi sea wind electric field again. After the filter is added, the harmonic currents of each order injected into the common connection point (poplar ditch door, 220kV bus) by the Wuqi sea wind electric field are calculated through simulation, and are compared with the limit value, and the comparison result is shown in table 4.
TABLE 4 comparison of injected harmonic current at 220kV common junction with a limit (filter)
Compared with the harmonic current of each time of the Wuhan sleeve sea wind electric field injected into the common connection point (the poplar ditch door and the 220kV bus) after the filter is added, the harmonic current is reduced in comparison with the harmonic current of each time of the Wuhan sleeve sea wind electric field injected into the common connection point before the filter is added, and the harmonic current is within an allowable range. Wherein, the 3 rd harmonic current is reduced to 1.7A from the original 5.7A.
The simulation calculation analysis shows that the active filter designed by the invention effectively reduces the harmonic current component injected into the power grid by the Wuqi sea wind power plant, reduces the content rate of each harmonic voltage and the total harmonic voltage distortion rate, and ensures that the harmonic influence caused by the wind power plant access system conforms to the national harmonic standard.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (5)
1. A harmonic wave analysis and treatment method for grid connection of a double-fed wind generating set is characterized by comprising the following steps:
the method comprises the following steps: constructing an electromagnetic transient model of the doubly-fed wind generating set based on the mathematical model of the doubly-fed wind generating set;
the electromagnetic transient model of the double-fed wind generating set comprises a generator converter model, a wind transmission shaft control model, a pitch angle control model and an electrical control model;
the generator converter model comprises an active control channel and a reactive control channel, wherein the active control channel takes an excitation voltage control signal obtained by calculation of the electrical control model as an input signal and outputs an active current signal; the reactive control channel takes an active current control signal obtained by calculation of the electrical control model as an input signal and outputs a reactive current signal;
the wind power transmission shaft control model comprises an impeller rotational inertia part and a generator rotational inertia part, the impeller and the generator are connected through a spring, the pneumatic power from the impeller and the electromagnetic power from the generator are used as two inputs, and the speed deviation of the impeller and the generator rotor is obtained under the regulation of a pitch angle; the pitch angle control model comprises a front half part and a rear half part, wherein the front half part is controlled by the rotating speed omega of the generatorgAs an input signal, a pitch control signal is given through a PI control link, and the power P of the generator is usedordThe back half takes the sum of the pitch control signal and the pitch compensation signal as input, and outputs a pitch angle β through a PI control integration link;
in the pitch angle control model, when power P transmitted to the generatorordGreater than PMXOr generator speed omegagWhen the rotational speed is greater than the reference value of the rotational speed, windThe force generator set increases the pitch angle in a fast pitch changing mode so as to reduce the rotating speed of the generator;
the electric control model comprises a WPMS model, an excitation controller and a power factor controller, wherein the WPMS model simulates voltage reactive power control of a wind power plant, the excitation controller simulates a converter/excitation system, and the power factor controller monitors the power factor of a fan grid-connected point;
step two: performing electromagnetic transient simulation calculation on the wind power plant by using an ADPSS simulation system to obtain harmonic current and harmonic voltage injected into a power grid by the wind power plant; step three: comparing the obtained harmonic current and harmonic voltage of the wind power plant input power grid with limit values respectively, and judging whether the harmonic current or the harmonic voltage of the wind power plant input power grid exceeds the standard or not;
step four: and if the harmonic current input into the power grid of the wind power plant exceeds the standard, designing an active filter, establishing a wind power plant electromagnetic transient model containing the active filter, and verifying the treatment effect of the harmonic current.
2. The harmonic analysis and treatment method for grid connection of the doubly-fed wind generating set according to claim 1, wherein the mathematical model of the doubly-fed wind generating set is as follows:
wherein, the stator and rotor flux linkage is expressed as:
the electromagnetic torque and the rotor motion equation of the generator are as follows:
TJps＝Tm-Te
in the formula, p represents a differential operator; subscripts s and r denote the stator of the motor, respectivelyA stator and a rotor, Ls、Lr、LmThe self inductance of the stator and the rotor and the mutual inductance between the stator and the rotor are respectively; subscripts d, q represent the quantities on the d-axis and q-axis, respectively, in dq0 coordinates; u, i,
R represents voltage, current, flux linkage and resistance, respectively; omega is the angular speed of the rotor; s is slip; t iseIs an electromagnetic torque; t ismIs the generator mechanical torque; t isJIs the rotor inertia time constant.
3. The method for analyzing and governing the harmonic wave of the grid connection of the doubly-fed wind generating set according to claim 1, wherein the method for calculating the harmonic wave current injected into the grid by the wind farm comprises the following steps:
calculating a harmonic current limit value allowed to be injected into a power grid after the wind power plant is accessed;
according to the established electromagnetic transient model of the double-fed wind generating set, carrying out simulation calculation by adopting an ADPSS simulation platform to obtain a current waveform flowing to a grid-connected point by a wind power plant on a line;
carrying out discrete Fourier transform on the current waveform obtained by simulation to obtain a harmonic current value injected into a power grid by the wind power plant;
and comparing the harmonic current value injected into the power grid by the wind power plant with the harmonic current limit value, if the harmonic current value is smaller than the harmonic current limit value, the harmonic current value is qualified, and otherwise, the harmonic current value is considered as exceeding the standard.
4. The method for analyzing and governing the harmonic waves of the grid connection of the doubly-fed wind generating set according to claim 1, wherein the method for calculating the harmonic voltage injected into the grid by the wind farm comprises the following steps:
according to the power quality-public power grid harmonic regulation standard, calculating the power grid subharmonic voltage content and the voltage total harmonic distortion rate generated at a grid-connected point by the harmonic current injected into the power grid by the wind power plant; wherein:
the content rate of each harmonic voltage of the power grid is as follows:
in the formula of UNIs the nominal voltage of the grid; skThree-phase short circuit capacity of a common connection point; i ishIs the h harmonic current;
the total harmonic distortion rate of the voltage is:
in the formula, HRUhThe h-th harmonic voltage content;
comparing the content of each harmonic voltage of the power grid caused by the harmonic current injected into the power grid by the wind power plant at the common point with the content limit value of each harmonic voltage of the power grid, if the former is smaller than the latter, the qualification is represented, otherwise, the standard exceeding is regarded;
and comparing the total voltage harmonic distortion rate caused by the harmonic voltage of the wind power plant input power grid at the common point with the total voltage harmonic distortion rate limit value, if the former is smaller than the latter, the result is qualified, and otherwise, the result is regarded as exceeding the standard.
5. The harmonic analysis and treatment method for grid connection of the doubly-fed wind generating set according to claim 1, wherein the method for designing the active filter and establishing the wind power plant electromagnetic transient model containing the active filter comprises the following steps:
filtering out harmonic current of the exceeding times generated by the wind turbine generator, designing an active filter based on the harmonic current generated by the wind turbine generator, additionally installing the filter on the booster station side of the wind farm, and establishing an electromagnetic transient model of the wind farm additionally provided with the active filter.
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| JP2019549529A JP6991233B2 (en) | 2018-06-20 | 2019-06-20 | Harmonic analysis and maintenance method for dual power supply type wind power generator set grid interconnection |
| PCT/CN2019/091990 WO2019242666A1 (en) | 2018-06-20 | 2019-06-20 | Harmonic analysis and treatment method for doubly-fed wind power generator set grid-connection |
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| CN109617076B (en) * | 2018-12-29 | 2020-09-18 | 燕山大学 | Voltage detection type active filter for improving electric energy quality at PCC |
| CN109980632B (en) * | 2019-02-15 | 2022-11-15 | 中国汽车工业工程有限公司 | Method for calculating allowed value of electric energy quality interference of low-voltage distribution network of whole plant |
| CN109870609B (en) * | 2019-03-01 | 2021-03-23 | 中国船舶重工集团海装风电股份有限公司 | Method, device, equipment and medium for detecting harmonic waves between double-fed wind turbine units |
| CN110887993A (en) * | 2019-11-14 | 2020-03-17 | 新奥数能科技有限公司 | Power harmonic detection and treatment analysis method and device |
| CN111987956B (en) * | 2020-08-10 | 2021-10-15 | 沈阳工业大学 | Torque ripple suppression method for direct-drive wind turbine generator |
| CN113032968B (en) * | 2021-03-02 | 2023-10-31 | 国网冀北电力有限公司电力科学研究院 | Double-fed fan controller parameter identification method and device |
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| CN115061384B (en) * | 2022-05-11 | 2023-09-08 | 国网山东省电力公司电力科学研究院 | Method for constructing semi-physical simulation electromagnetic model of single-motor double-unit direct-driven fan |
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