CN113489070B - Flexible-straight parameter intelligent optimization method and system for new energy grid connection - Google Patents
Flexible-straight parameter intelligent optimization method and system for new energy grid connection Download PDFInfo
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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
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
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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
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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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
- 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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
Abstract
The invention discloses a flexible-straight parameter intelligent optimization method and system for new energy grid connection, and belongs to the technical field of system stability optimization. The method of the invention comprises the following steps: determining key parameters of large-scale new energy island access flexible direct system; collecting instantaneous active power and reactive power of a large-scale new energy island at a grid-connected point of a flexible direct system in real time, and extracting characteristic components according to the instantaneous active power and the reactive power; setting key parameters of the intelligent optimization algorithm according to the operation condition of the system, and judging whether the system meets the input condition of the intelligent optimization algorithm according to the characteristic components; and if so, dynamically adjusting the proportion parameters of the external loop proportion-integral controller of the flexible direct island converter station by adopting the intelligent optimization method according to the system operation condition until the characteristic components meet the exit condition of the intelligent optimization algorithm, so as to realize the system stability. The invention can monitor the running state of the system in real time when 8-15 Hz oscillation occurs due to mismatching of control parameters during the flexible direct grid connection of large-scale new energy.
Description
Technical Field
The invention relates to the technical field of system stability optimization, in particular to a flexible-straight parameter intelligent optimization method and system for new energy grid connection.
Background
Along with clean transformation of world energy power, new energy is rapidly developed, and the installed capacity is continuously increased. The new energy power generation, direct current transmission technology, variable frequency load and other power electronic equipment are applied to a large number of source-network-load, and the power electronization degree of a power system and the influence caused by the power electronization degree are continuously increased.
The flexible direct current transmission technology is a new generation transmission technology, has the advantages of flexibility and controllability, high reliability, island power supply and the like compared with the traditional transmission technology based on the grid commutation converter, and is suitable for the construction of large-scale new energy efficient acceptance, regional power transmission networks such as large cities, islands and the like and efficient power transmission and distribution networks. At present, flexible direct current transmission is an important implementation mode for large-scale and new centralized power transmission on land and at sea.
In a large-scale new energy soft direct-delivery scene, the interaction influence among a soft direct-current transmission system, an alternating-current power grid and a new energy station is very easy to cause system oscillation. For example, subsynchronous oscillation of voltage and current occurs in the south-sink flexible direct current transmission project, the south-Australian flexible direct current transmission project and the mansion flexible direct current transmission project in the output change process of a wind power plant; intermediate frequency oscillation of 250-350 Hz occurs in the BorWin1 project sent out by the soft and straight wind farm in the North sea in Germany, and core components are burnt out, so that the wind farm is shut down for a long time, and huge economic loss is caused; in the robust back-to-back soft-direct project, 1270Hz high frequency oscillation occurs when the multi-circuit ac transmission line is disconnected; in the Zhang Beirou direct-current power grid debugging process, after the island of the converter station is unlocked and locked on a grid side switch, high-frequency oscillation occurs on grid side voltage to cause system tripping, locking faults occur in the operation of a festive monopole, short-time severe overvoltage of a sending end island system is caused by surplus power of new energy after an energy consumption resistor exits, different degrees of damage occur on equipment of a middle-rise station and the new energy station, and the new energy is totally off-grid.
In the digital-analog mixed real-time simulation research of a large-scale new energy output system of a Zhang Beirou direct-current power grid, the oscillation phenomenon of about 10Hz occurs when the new energy is sent out of the grid alternating voltage in the power rising process of a photovoltaic station and a doubly-fed fan station of an island access Zhang Bei converter station.
With the development of onshore and offshore wind power in China, the oscillation risk of a new energy conveying system is gradually increased through the increase of the flexible and straight outward-conveying capacity of new energy, and the safety and the stability of a power grid at a transmitting and receiving end are greatly threatened.
At present, proper control parameters are selected in the initial stage of designing a system of a flexible direct-connected system by adopting a time domain simulation analysis method or a frequency domain impedance analysis method and the like, so as to avoid system resonance points. The off-line oscillation suppression method relies on an accurate new energy station equivalent model. However, the running state of the static reactive power compensation device (static var generator, SVG) configured in the new energy station and the parameter error of the collecting line can all affect the system resonance point, so that the suppression effect after parameter optimization is seriously affected.
Disclosure of Invention
Aiming at the problems, the invention provides a flexible-direct parameter intelligent optimization method for new energy grid connection, which comprises the following steps:
determining key parameters of large-scale new energy island access flexible direct system;
collecting instantaneous active power and reactive power of a large-scale new energy island at a grid-connected point of a flexible direct system in real time, and extracting characteristic components according to the instantaneous active power and the reactive power;
setting key parameters of the intelligent optimization algorithm according to the operation condition of the system, and judging whether the system meets the input condition of the intelligent optimization algorithm according to the characteristic components;
and if so, dynamically adjusting the proportion parameters of the external loop proportion-integral controller of the flexible direct island converter station by adopting the intelligent optimization method according to the system operation condition until the characteristic components meet the exit condition of the intelligent optimization algorithm, so as to realize the system stability.
Optionally, the key parameters comprise an apparent power threshold, an oscillation component upper limit threshold, an oscillation component lower limit threshold, a control period, an initial value of a proportion parameter of an outer loop proportional-integral controller of the flexible direct island converter station, an adjustment lower limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station and an adjustment upper limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station.
Optionally, the feature component includes: the frequency and content of the oscillating component, the average apparent power;
the characteristic component is extracted according to instantaneous active power and reactive power, and specifically comprises the following steps:
and performing fast Fourier transform on the instantaneous active power and the instantaneous reactive power to acquire the frequency and the content of an oscillation component, and acquiring the average apparent power of new energy sent by a preset number of fundamental wave periods by using a sliding window average method on the instantaneous active power and the instantaneous reactive power.
Optionally, determining whether the feature component satisfies the input condition or the exit condition includes:
determining whether a per unit value of the average apparent power is greater than or equal to an apparent power threshold, if so, determining whether the frequency of the oscillation component meets a preset range and whether the ratio of the content of the oscillation component to the average apparent power meets an overrun upper limit threshold or not by using a system transmission power permission mark position 1, and if so, using the oscillation component overrun mark position 1, and when the system transmission power permission mark position and the oscillation component overrun mark position are simultaneously 1, enabling the characteristic component to meet an input condition;
and determining whether the per unit value of the average apparent power is smaller than an apparent power threshold value, if so, determining whether the ratio of the content of the oscillating component to the average apparent power is smaller than a lower limit threshold value by using a system transmission power permission mark position 0, and if so, using an oscillating component out-of-limit mark position 0, and when the system transmission power permission mark position and the oscillating component out-of-limit mark position are simultaneously 0, enabling the characteristic component to meet an exit condition.
Optionally, the optimizing algorithm exits from the condition, including: the exit condition is satisfied, the value satisfying the proportion parameter exceeds the adjustment upper limit value of the proportion parameter, or the value satisfying the proportion parameter is lower than the adjustment lower limit value of the proportion parameter.
Optionally, adjusting the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station until the characteristic component meets the input condition or the exit condition of the intelligent optimization algorithm, including:
and (3) increasing the value of the proportion parameter, determining whether the ratio of the content of the oscillation component to the average apparent power is smaller, if so, continuing to increase the value of the proportion parameter until the characteristic component meets the system stability condition, and if not, reducing the value of the proportion parameter until the characteristic component meets the input condition or the exit condition of the intelligent optimization algorithm.
The invention also provides a flexible-straight parameter intelligent optimization system for new energy grid connection, which comprises the following steps:
the key parameter determining module is used for determining key parameters of the large-scale new energy island access flexible direct system;
the characteristic component extraction module is used for collecting instantaneous active power and reactive power of a grid-connected point of the large-scale new energy island access flexible direct system in real time and extracting characteristic components according to the instantaneous active power and the reactive power;
the adjusting module is used for adjusting key parameters of the intelligent optimization algorithm according to the system operation condition and judging whether the input condition of the intelligent optimization algorithm is met or not according to the characteristic components; and if so, adjusting the proportion parameters of the outer loop proportional-integral controller of the flexible direct island converter station until the characteristic components meet the exit condition of the intelligent optimization algorithm.
Optionally, the key parameters comprise an apparent power threshold, an oscillation component upper limit threshold, an oscillation component lower limit threshold, a control period, an initial value of a proportion parameter of an outer loop proportional-integral controller of the flexible direct island converter station, an adjustment lower limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station and an adjustment upper limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station.
Optionally, the feature component includes: the frequency and content of the oscillating component, the average apparent power;
the characteristic component is extracted according to the instantaneous power and the reactive power, and specifically comprises the following steps:
and performing fast Fourier transform on the instantaneous active power and the instantaneous reactive power to acquire the frequency and the content of an oscillation component, and acquiring the average apparent power of new energy sent by a preset number of fundamental wave periods by using a sliding window average method on the instantaneous active power and the instantaneous reactive power.
Optionally, determining whether the feature component satisfies the input condition or the exit condition includes:
determining whether a per unit value of the average apparent power is greater than or equal to an apparent power threshold, if so, determining whether the frequency of the oscillation component meets a preset range and whether the ratio of the content of the oscillation component to the average apparent power meets an overrun upper limit threshold or not by using a system transmission power permission mark position 1, and if so, using the oscillation component overrun mark position 1, and when the system transmission power permission mark position and the oscillation component overrun mark position are simultaneously 1, enabling the characteristic component to meet an input condition;
and determining whether the per unit value of the average apparent power is smaller than an apparent power threshold value, if so, determining whether the ratio of the content of the oscillating component to the average apparent power is smaller than a lower limit threshold value by using a system transmission power permission mark position 0, and if so, using an oscillating component out-of-limit mark position 0, and when the system transmission power permission mark position and the oscillating component out-of-limit mark position are simultaneously 0, enabling the characteristic component to meet an exit condition.
Optionally, the optimizing algorithm exits from the condition, including: the exit condition is satisfied, the value satisfying the proportion parameter exceeds the adjustment upper limit value of the proportion parameter, or the value satisfying the proportion parameter is lower than the adjustment lower limit value of the proportion parameter.
Optionally, adjusting the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station until the characteristic component meets the input condition or the exit condition of the intelligent optimization algorithm, including:
and (3) increasing the value of the proportion parameter, determining whether the ratio of the content of the oscillation component to the average apparent power is smaller, if so, continuing to increase the value of the proportion parameter until the characteristic component meets the system stability condition, and if not, reducing the value of the proportion parameter until the characteristic component meets the input condition or the exit condition of the intelligent optimization algorithm.
According to the invention, when the large-scale new energy source is in flexible direct grid connection, and 8-15 Hz oscillation occurs due to mismatching of control parameters, the running state of the system can be monitored in real time, and the optimal parameter matched with the actual running state of the system is found by intelligently optimizing the proportional parameters of the outer ring proportional-integral controller of the direct island converter station, so that the effect of suppressing the oscillation is achieved.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a flow chart of an embodiment of the method of the present invention;
FIG. 3 is a schematic diagram of a simulation model sent out by a large-scale new energy source through soft direct grid connection in an embodiment of the method of the invention;
fig. 4 is a waveform diagram of active power per unit value, reactive power per unit value and grid-connected point voltage per unit value of the post-new energy station 1 in the embodiment of the method of the present invention;
fig. 5 is a waveform diagram of active power per unit value, reactive power per unit value and grid-connected point voltage per unit value of the post-new energy station 2 in the embodiment of the method of the present invention;
FIG. 6 is a waveform diagram of the AC current and AC voltage of the post-soft direct-current grid-connected point in an embodiment of the method of the present invention;
FIG. 7 is a graph showing the waveforms of active power and reactive power at the post-soft direct grid connection point in an embodiment of the method of the present invention;
FIG. 8 is a waveform diagram of the variation curve of the Kp value of the post-straightening parameter, the cutting identification bit of the optimizing algorithm input and the effective value of the oscillation component in the embodiment of the method of the invention;
fig. 9 is a block diagram of the system of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the examples described herein, which are provided to fully and completely disclose the present invention and fully convey the scope of the invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like elements/components are referred to by like reference numerals.
Unless otherwise indicated, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, it will be understood that terms defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
The invention provides a flexible direct parameter intelligent optimization method for new energy grid connection, which is shown in fig. 1 and comprises the following steps:
determining key parameters of large-scale new energy island access flexible direct system;
collecting instantaneous active power and reactive power of a large-scale new energy island at a grid-connected point of a flexible direct system in real time, and extracting characteristic components according to the instantaneous active power and the reactive power;
setting key parameters of the intelligent optimization algorithm according to the operation condition of the system, and judging whether the system meets the input condition of the intelligent optimization algorithm according to the characteristic components;
and if so, dynamically adjusting the proportion parameters of the external loop proportion-integral controller of the flexible direct island converter station by adopting the intelligent optimization method according to the system operation condition until the characteristic components meet the exit condition of the intelligent optimization algorithm, so as to realize the system stability.
The key parameters comprise an apparent power threshold, an oscillation component upper limit threshold, an oscillation component lower limit threshold, a control period, an initial value of a proportion parameter of an outer loop proportional-integral controller of the flexible direct island converter station, an adjustment lower limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station and an adjustment upper limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station.
Wherein the feature components include: the frequency and content of the oscillating component, the average apparent power;
the characteristic component is extracted according to the instantaneous power and the reactive power, and specifically comprises the following steps:
and performing fast Fourier transform on the instantaneous active power and the instantaneous reactive power to acquire the frequency and the content of an oscillation component, and acquiring the average apparent power of new energy sent by a preset number of fundamental wave periods by using a sliding window average method on the instantaneous active power and the instantaneous reactive power.
Wherein determining whether the feature component satisfies the input condition or the exit condition includes:
determining whether a per unit value of the average apparent power is greater than or equal to an apparent power threshold, if so, determining whether the frequency of the oscillation component meets a preset range and whether the ratio of the content of the oscillation component to the average apparent power meets an overrun upper limit threshold or not by using a system transmission power permission mark position 1, and if so, using the oscillation component overrun mark position 1, and when the system transmission power permission mark position and the oscillation component overrun mark position are simultaneously 1, enabling the characteristic component to meet an input condition;
and determining whether the per unit value of the average apparent power is smaller than an apparent power threshold value, if so, determining whether the ratio of the content of the oscillating component to the average apparent power is smaller than a lower limit threshold value by using a system transmission power permission mark position 0, and if so, using an oscillating component out-of-limit mark position 0, and when the system transmission power permission mark position and the oscillating component out-of-limit mark position are simultaneously 0, enabling the characteristic component to meet an exit condition.
The method for adjusting the proportion parameters of the outer loop proportional-integral controller of the flexible direct island converter station until the characteristic components meet the input condition or the exit condition of the intelligent optimization algorithm comprises the following steps:
and (3) increasing the value of the proportion parameter, determining whether the ratio of the content of the oscillation component to the average apparent power is smaller, if so, continuing to increase the value of the proportion parameter until the characteristic component meets the system stability condition, and if not, reducing the value of the proportion parameter until the characteristic component meets the input condition or the exit condition of the intelligent optimization algorithm.
The invention is further illustrated by the following examples:
the invention takes active power and reactive power of a large-scale new energy island connected to a soft direct grid-connected point as controlled objects, extracts oscillation characteristic quantity, and intelligently optimizes the proportion parameter Kp of an outer loop proportional-integral controller of the soft direct island converter station on line when the oscillation component exceeds a limit value, thereby inhibiting the oscillation component and performing intelligent optimization, and the specific steps are as shown in figure 2 and include:
step 1, extracting oscillation characteristic components and setting key parameters in an oscillation suppression algorithm;
the instantaneous active power and the instantaneous reactive power at the point of connection are acquired in real time through the soft direct control protection system, the acquired instantaneous active power and the acquired instantaneous reactive power are subjected to fast Fourier transform, the frequency and the content of an oscillation component are calculated, and the calculated average apparent power sent by the new energy source in 10 fundamental wave periods is calculated by adopting a sliding window average method.
The key parameters in the invention mainly comprise: apparent power threshold S th Oscillation component upper limit threshold SSO up_th Oscillation component lower limit threshold SSO down_th Control period T c Initial value Kp of Kp init Kp adjustment lower limit DK pmin Kp adjustment upper limit DK pmax 。
Step 2, judging input conditions of the large-scale new energy source after the soft direct grid connection stability;
and (3) judging whether the per unit value of the current average apparent power is larger than or equal to an apparent power threshold in real time according to the apparent power calculated in the step (1), if the per unit value of the current average apparent power is larger than or equal to the apparent power threshold, transmitting the system to a power permission mark position (1), judging whether the frequency is in the range of 8-15 Hz according to the frequency and the content of the oscillation component extracted in the step (1), calculating whether the ratio of the effective value of the current oscillation component to the average apparent power exceeds an upper limit threshold, and if the ratio exceeds the upper limit threshold, judging the oscillation component to exceed the limit mark position (1). When the system transmission power permission flag position and the oscillation component out-of-limit flag position are 1 at the same time, the input is made.
Step 3, judging the exit condition of the large-scale new energy source after the soft direct grid connection stability;
and (3) judging whether the per unit value of the current average apparent power is smaller than an apparent power threshold value in real time according to the apparent power calculated in the step (1), and if the per unit value of the current average apparent power is smaller than the apparent power threshold value, transmitting the power permission mark position 0 of the system. And (3) calculating whether the ratio of the current oscillation component to the average apparent power is smaller than a lower limit threshold according to the amplitude of the oscillation component extracted in the step (1), and if so, marking the oscillation component out-of-limit as 0. When the system transmission power permission flag position or the oscillation component out-of-limit flag position is simultaneously 0, the method exits.
Step 4, optimizing the stability of the new energy system;
on the basis of the initial value of the proportion parameter Kp of the flexible straight island converter station outer loop proportion-integral controller set in the step 1, increasing DKp the proportion parameter Kp, observing whether the ratio of the oscillation component to the average apparent power becomes smaller, if so, continuously increasing the Kp value until the exit condition of the step 3 is met or the Kp value exceeds the adjustment upper limit value; if not, the Kp value is reduced until the exit condition of step 3 is satisfied or the Kp value is below the adjustment lower limit.
In step 1, the apparent power threshold S th Set at 5% of rated apparent power, the oscillation component upper limit threshold SSO up_th And a lower threshold SSO down_th All are set according to 0.133%, the control period Tc is set according to 500ms, and the Kp initial value Kp is set init Setting according to a traditional oscillation suppression method, and adjusting a lower limit Kp by Kp min And an upper limit Kp max Respectively according to Kp initial value Kp init Is set by 0.5 times and 3 times, kp adjusts the step DK p According to 0.067Kp init Setting.
The invention is applied to the digital-analog hybrid simulation research of the north-opening large-scale new energy island through soft and direct delivery, and based on a new algebraic-analog hybrid simulation platform of the north-opening-Beijing end-to-end soft and direct control device of the north-opening engineering, a hardware-in-loop real-time simulation model with a new energy delivery grid structure shown in fig. 3 is built, the total installed capacity of two wind power plants is 500MW, and the rated capacity of a soft and direct converter is Srate=1500 MW.
According to the above assumption, the setting values of the key parameters are: apparent power threshold S th =5% oscillation component upper threshold SSO up_th =0.133%, lower threshold SSO down_th =0.133%, control period T c =500ms, kp initial value Kp init =0.3, kp adjusts the lower limit Kp min =0.15，Kp max =0.9 kp adjustment step DK p =0.067Kp init 。
The method comprises the following specific steps:
1. real-time acquisition of instantaneous active power and instantaneous reactive power at the point of connection by a soft direct control protection system, fast Fourier transformation of the acquired instantaneous active power and instantaneous reactive power, calculation of frequency fsSO of oscillation component and effective value AmSSO=max (P AM ,Q AM )，P AM As effective value of active power oscillation component, Q AM And calculating the calculated average apparent power Save of the new energy source output in 10 fundamental wave periods by adopting a sliding window average method as an effective value of the reactive power oscillation component.
Real-time judging current average apparent power per unit value S ave_pu =S ave /S rate Whether or not it is equal to or greater than the apparent power threshold S th =5%, if the condition is satisfied, the system transmission power permission flag is set at position 1, and according to the oscillation component effective value AmSSO extracted in step 1, whether the ratio of the current oscillation component AmSSO to the average apparent power Save exceeds the upper limit threshold SSO is calculated up_th =0.133%, and if out of limit, the oscillation component is out of limit by flag position 1. When the system transmission power permission flag position and the oscillation component out-of-limit flag position are 1 at the same time, the input is made.
After the suppression algorithm is put into operation, the initial value Kp of the proportion parameter Kp of the outer ring proportion-integral controller of the flexible direct island converter station init On the basis of =0.3, the ratio parameter Kp is increased by DK p ，DK p =0.067Kp init Observing whether the ratio of the oscillation component to the average apparent power is smaller, if so, continuing to increase the Kp value until the exit condition of the step 3 is met or the Kp value exceeds the adjustment upper limit value; if not, the Kp value is reduced until the exit condition of step 3 is satisfied or the Kp value is below the adjustment lower limit.
Real-time judging current average viewAt the per-unit value S of power ave_pu =S ave /S rate Whether or not it is smaller than the apparent power threshold S th =5%, and if the condition is satisfied, the system transmission power grant flag is set to position 0. Calculating the current oscillation component AmSSO and the average apparent power S ave Whether the ratio of (2) is less than the lower threshold SSO down_th =0.133%, and if out of limit, the oscillation component out of limit flag position 0. When the system transmission power permission flag position or the oscillation component out-of-limit flag position is simultaneously 0, the method exits.
The simulation analysis of the embodiment of the flexible straight parameter intelligent optimization method suitable for improving the stability of the new energy source conveying system is as follows:
without the intelligent optimization algorithm of the invention, kp=kp init When the output of the new energy source is increased to 196MW, the system generates oscillation with the frequency of 10.2Hz, and the oscillation component effective value P of the active power of the new energy source grid-connected point AM About 8.3MW, oscillation component effective value Q of reactive power AM About 7.6MW, the active power, reactive power and alternating voltage of the wind power plant and the on-line alternating voltage, alternating current, active power and reactive power of the flexible direct island converter station all oscillate, and at the moment, the average apparent power per unit value S ave_pu =S ave /S rate =196 MW/1500=13.1% greater than or equal to the apparent power threshold S th =5%, system transmission power grant flag position 1; oscillation component effective value amsso=max (P AM ,Q AM ) =8.3 MW, and average apparent power S ave Is 0.553% above the upper threshold SSO up_th =0.133%, oscillation component out-of-limit flag position 1. And 4-8, after the intelligent optimization algorithm is input, when the proportion parameter Kp of the external loop proportional-integral controller of the flexible direct island converter station is regulated to 0.6, the active power, reactive power and alternating voltage of the wind power plant are rapidly attenuated, and the system is stable. When the ratio of the oscillation component effective value AmSSO to the average apparent power Save is smaller than the lower threshold SSO down_th =0.133%, and the soft-straight parameter intelligent optimization algorithm exits, and finally oscillatesThe component effective value AmSSO approaches 0 and the oscillation disappears.
From the simulation calculation results, it is easy to know that the flexible-straight parameter intelligent optimization method suitable for improving the stability of the system for conveying the new energy uses the power of the large-scale new energy which is connected to the grid-connected point through the flexible-straight island as a detection object, and judges the oscillation state of the system by extracting oscillation characteristic components. When the system oscillates, the proportion parameter Kp of the external loop proportion-integral controller of the flexible direct island converter station is intelligently adjusted, 8-15 Hz oscillation can be effectively restrained, the system is enabled to be restored to be stable, safe operation of the flexible direct island converter and the new energy unit is guaranteed, secondary damage caused by system oscillation propagation is avoided, and safety and reliability of a large-scale new energy grid-connected system through flexible direct island are improved.
The invention also provides a flexible-straight parameter intelligent optimization system 200 for new energy grid connection, as shown in fig. 9, comprising:
the key parameter determining module 201 determines key parameters of the large-scale new energy island access flexible direct system;
the characteristic component extraction module 202 is used for collecting instantaneous active power and reactive power at grid-connected points of the large-scale new energy island access flexible direct system in real time and extracting characteristic components according to the instantaneous active power and the reactive power;
the adjusting module 203 adjusts key parameters of the intelligent optimization algorithm according to the system operation condition, and determines whether the characteristic components meet the input condition or the exit condition of the intelligent optimization algorithm; and if the characteristic component meets the input condition or the exit condition of the intelligent optimization algorithm, adjusting the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station.
The key parameters comprise an apparent power threshold, an oscillation component upper limit threshold, an oscillation component lower limit threshold, a control period, an initial value of a proportion parameter of an outer loop proportional-integral controller of the flexible direct island converter station, an adjustment lower limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station and an adjustment upper limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station.
Wherein the feature components include: the frequency and content of the oscillating component, the average apparent power;
the characteristic component is extracted according to the instantaneous power and the reactive power, and specifically comprises the following steps:
and performing fast Fourier transform on the instantaneous active power and the instantaneous reactive power to acquire the frequency and the content of an oscillation component, and acquiring the average apparent power of new energy sent by a preset number of fundamental wave periods by using a sliding window average method on the instantaneous active power and the instantaneous reactive power.
Wherein determining whether the feature component satisfies the input condition or the exit condition includes:
determining whether a per unit value of the average apparent power is greater than or equal to an apparent power threshold, if so, determining whether the frequency of the oscillation component meets a preset range and whether the ratio of the content of the oscillation component to the average apparent power meets an overrun upper limit threshold or not by using a system transmission power permission mark position 1, and if so, using the oscillation component overrun mark position 1, and when the system transmission power permission mark position and the oscillation component overrun mark position are simultaneously 1, enabling the characteristic component to meet an input condition;
and determining whether the per unit value of the average apparent power is smaller than an apparent power threshold value, if so, determining whether the ratio of the content of the oscillating component to the average apparent power is smaller than a lower limit threshold value by using a system transmission power permission mark position 0, and if so, using an oscillating component out-of-limit mark position 0, and when the system transmission power permission mark position and the oscillating component out-of-limit mark position are simultaneously 0, enabling the characteristic component to meet an exit condition.
Wherein the optimization algorithm exit condition comprises: the exit condition is satisfied, the value satisfying the proportion parameter exceeds the adjustment upper limit value of the proportion parameter, or the value satisfying the proportion parameter is lower than the adjustment lower limit value of the proportion parameter.
The method for adjusting the proportion parameters of the outer loop proportional-integral controller of the flexible direct island converter station until the characteristic components meet the input condition or the exit condition of the intelligent optimization algorithm comprises the following steps:
and (3) increasing the value of the proportion parameter, determining whether the ratio of the content of the oscillation component to the average apparent power is smaller, if so, continuing to increase the value of the proportion parameter until the characteristic component meets the system stability condition, and if not, reducing the value of the proportion parameter until the characteristic component meets the input condition or the exit condition of the intelligent optimization algorithm.
According to the invention, when the large-scale new energy source is in flexible direct grid connection, and 8-15 Hz oscillation occurs due to mismatching of control parameters, the running state of the system can be monitored in real time, and the optimal parameter matched with the actual running state of the system is found by intelligently optimizing the proportional parameters of the outer ring proportional-integral controller of the direct island converter station, so that the effect of suppressing the oscillation is achieved.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention 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 scheme in the embodiment of the invention can be realized by adopting various computer languages, such as object-oriented programming language Java, an transliteration script language JavaScript and the like.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations 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 processor, 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.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (6)
1. A flexible-straight parameter intelligent optimization method for new energy grid connection, the method comprising:
determining key parameters of large-scale new energy island access flexible direct system;
collecting instantaneous active power and reactive power of a large-scale new energy island at a grid-connected point of a flexible direct system in real time, and extracting characteristic components according to the instantaneous active power and the reactive power;
setting key parameters according to the system operation conditions, and determining whether the characteristic components meet the input conditions;
if the characteristic component meets the exit condition, adjusting the proportion parameter of an outer ring proportion-integral controller of the flexible direct island converter station until the characteristic component is determined to meet the exit condition, so as to realize system stability;
the key parameters comprise an apparent power threshold, an oscillation component upper limit threshold, an oscillation component lower limit threshold, a control period, an initial value of a proportion parameter of an outer loop proportional-integral controller of the flexible direct island converter station, an adjustment lower limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station and an adjustment upper limit value of the proportion parameter of the outer loop proportional-integral controller of the flexible direct island converter station;
the feature components include: the frequency and content of the oscillating component, the average apparent power;
the characteristic component is extracted according to instantaneous active power and reactive power, and specifically comprises the following steps:
performing fast Fourier transform on the instantaneous active power and the instantaneous reactive power to obtain the frequency and the content of an oscillation component, and obtaining the average apparent power of new energy sent by a preset number of fundamental wave periods on the instantaneous active power and the instantaneous reactive power by using a sliding window average method;
the determining whether the feature component satisfies the input condition or satisfies the exit condition includes:
determining whether a per unit value of the average apparent power is greater than or equal to an apparent power threshold, if so, determining whether the frequency of the oscillation component meets a preset range and whether the ratio of the content of the oscillation component to the average apparent power meets an overrun upper limit threshold or not by using a system transmission power permission mark position 1, and if so, using the oscillation component overrun mark position 1, and when the system transmission power permission mark position and the oscillation component overrun mark position are simultaneously 1, enabling the characteristic component to meet an input condition;
and determining whether the per unit value of the average apparent power is smaller than an apparent power threshold value, if so, determining whether the ratio of the content of the oscillating component to the average apparent power is smaller than a lower limit threshold value by using a system transmission power permission mark position 0, and if so, using an oscillating component out-of-limit mark position 0, and when the system transmission power permission mark position and the oscillating component out-of-limit mark position are simultaneously 0, enabling the characteristic component to meet an exit condition.
2. The method of claim 1, the feature component satisfying an exit condition, comprising: the exit condition is satisfied, the value satisfying the proportion parameter exceeds the adjustment upper limit value of the proportion parameter, or the value satisfying the proportion parameter is lower than the adjustment lower limit value of the proportion parameter.
3. The method of claim 1, wherein the adjusting the proportional parameter of the soft direct island converter station outer loop proportional-integral controller until the characteristic component meets the input condition or the exit condition comprises:
and (3) increasing the value of the proportion parameter, determining whether the ratio of the content of the oscillation component to the average apparent power is smaller, if so, continuing to increase the value of the proportion parameter until the characteristic component meets the system stability condition, and if not, reducing the value of the proportion parameter until the characteristic component meets the input condition or the exit condition.
4. A flexible-straight parameter intelligent optimization system for new energy grid connection, the system comprising:
the key parameter determining module is used for determining key parameters of the large-scale new energy island access flexible direct system;
the characteristic component extraction module is used for collecting instantaneous active power and reactive power of a grid-connected point of the large-scale new energy island access flexible direct system in real time and extracting characteristic components according to the instantaneous active power and the reactive power;
the adjusting module is used for adjusting the key parameters according to the system operation working conditions and determining whether the characteristic components meet the input conditions; if the characteristic component meets the exit condition, adjusting the proportion parameter of an outer ring proportion-integral controller of the flexible straight island converter station until the characteristic component is determined to meet the exit condition;
the key parameters comprise an apparent power threshold, an oscillation component upper limit threshold, an oscillation component lower limit threshold, a control period, an initial value of a proportional-integral controller of an outer loop of the flexible direct island converter station, an adjustment lower limit value of the proportional parameter of the outer loop proportional-integral controller of the flexible direct island converter station and an adjustment upper limit value of the proportional parameter of the outer loop proportional-integral controller of the flexible direct island converter station;
the feature components include: the frequency and content of the oscillating component, the average apparent power;
the characteristic component is extracted according to the instantaneous power and the reactive power, and specifically comprises the following steps:
performing fast Fourier transform on the instantaneous active power and the instantaneous reactive power to obtain the frequency and the content of an oscillation component, and obtaining the average apparent power of new energy sent by a preset number of fundamental wave periods on the instantaneous active power and the instantaneous reactive power by using a sliding window average method;
the determining whether the feature component satisfies the input condition or satisfies the exit condition includes:
determining whether a per unit value of the average apparent power is greater than or equal to an apparent power threshold, if so, determining whether the frequency of the oscillation component meets a preset range and whether the ratio of the content of the oscillation component to the average apparent power meets an overrun upper limit threshold or not by using a system transmission power permission mark position 1, and if so, using the oscillation component overrun mark position 1, and when the system transmission power permission mark position and the oscillation component overrun mark position are simultaneously 1, enabling the characteristic component to meet an input condition;
and determining whether the per unit value of the average apparent power is smaller than an apparent power threshold value, if so, determining whether the ratio of the content of the oscillating component to the average apparent power is smaller than a lower limit threshold value by using a system transmission power permission mark position 0, and if so, using an oscillating component out-of-limit mark position 0, and when the system transmission power permission mark position and the oscillating component out-of-limit mark position are simultaneously 0, enabling the characteristic component to meet an exit condition.
5. The system of claim 4, the feature component satisfying an exit condition comprising: the exit condition is satisfied, the value satisfying the proportion parameter exceeds the adjustment upper limit value of the proportion parameter, or the value satisfying the proportion parameter is lower than the adjustment lower limit value of the proportion parameter.
6. The system of claim 4, the adjusting the proportional parameter of the flexible direct island converter station outer loop proportional-integral controller until the characteristic component meets the put-in condition or the withdraw condition, comprising:
and (3) increasing the value of the proportion parameter, determining whether the ratio of the content of the oscillation component to the average apparent power is smaller, if so, continuing to increase the value of the proportion parameter until the characteristic component meets the system stability condition, and if not, reducing the value of the proportion parameter until the characteristic component meets the input condition or the exit condition.
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