CN114421533A - Method for transforming virtual synchronous machine of fan based on idea of virtual synchronous machine - Google Patents

Method for transforming virtual synchronous machine of fan based on idea of virtual synchronous machine Download PDF

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CN114421533A
CN114421533A CN202111525940.9A CN202111525940A CN114421533A CN 114421533 A CN114421533 A CN 114421533A CN 202111525940 A CN202111525940 A CN 202111525940A CN 114421533 A CN114421533 A CN 114421533A
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synchronous machine
virtual synchronous
wind turbine
control
fan
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卢广陵
周柯
孙志媛
窦骞
张翌晖
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Electric Power Research Institute of Guangxi Power Grid Co Ltd
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Electric Power Research Institute of Guangxi Power Grid Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • H02J3/42—Synchronising a generator for connection to a network or to another generator with automatic parallel connection when synchronisation is achieved
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • 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]
    • 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

Abstract

The invention discloses a method for transforming a virtual synchronous machine of a fan based on the idea of the virtual synchronous machine, which relates to the technical field of virtual synchronous machines of fans, and judges whether the variable speed fan can transform the virtual synchronous machine or not by analyzing the operating characteristics of various variable speed fans; and selecting a variable speed fan capable of carrying out virtual synchronous machine transformation to carry out strategy analysis, and setting virtual synchronous machine control according to an analysis result so as to complete the transformation of the virtual synchronous machine of the fan. The new energy machine set applying the virtual synchronous machine technology can change the frequency response characteristic of equipment and has the functions of adjusting the voltage and the frequency of a system, providing damping and the like by reasonably configuring the control parameters of the virtual synchronous machine, thereby participating in the dynamic adjustment of the system and improving the operation safety and stability level of a power grid to a certain extent. The virtual synchronous generator technology provides a new solution for a new energy-friendly grid-connected mode.

Description

Method for transforming virtual synchronous machine of fan based on idea of virtual synchronous machine
Technical Field
The invention belongs to the technical field of virtual synchronous machines of fans, and particularly relates to a virtual synchronous machine transformation method of a fan based on the idea of a virtual synchronous machine.
Background
With the gradual increase of the proportion of the machine loading capacity of the wind power in the power system and the rapid increase of various power loads, the characteristics of a power supply and a power grid are deeply changed, and the influence on the power system is gradually highlighted. The continuous improvement of the permeability of new energy and the direct current receiving ratio gradually reduces the installed ratio of the traditional synchronous generator, the rotary reserve capacity and the rotary inertia in the power system are relatively reduced, the inertia and the primary frequency modulation capability of the synchronous power grid are continuously reduced, risks are brought to the frequency stability and the recovery capability of the system under the high-power shortage impact, and pressure is brought to the safe and stable operation of the power system. The frequency problem is particularly prominent in the receiving end power grid.
In recent years, a new energy grid-connection concept of 'power grid-friendly' is proposed, and the research of the power grid-friendly power generation technology emphasizes active participation, flexible interaction and high coordination of power equipment at present. In the aspect of new energy power generation, the predictability, the adjustability, the controllability and the stability are improved, and the capability of a power grid for receiving fluctuating new energy and the safe and economic operation capability are improved. The conventional synchronous generator has natural friendly characteristics to a power grid, and if the operation experience of a traditional power system can be used for reference and a related control strategy and analysis method of the conventional synchronous generator are effectively introduced, the grid-connected inverter has the operation characteristics similar to those of the synchronous generator, the adjustability, the controllability and the stability are improved, the friendly access of distributed new energy resources can be realized, and the stability of the power system is improved. Based on the thought, scholars at home and abroad propose a Virtual Synchronous Generator (VSG) technology, so that the grid-connected inverter can simulate the operation mechanism of the synchronous generator.
At present, the research and application of a virtual synchronous generator in the aspect of new energy grid connection are still in a starting state, and the understanding of the academic and industrial circles on the functions of the virtual synchronous generator and the specific application of the virtual synchronous generator in a large power grid have some inconsistent and unclear points, so that a method for modifying a virtual synchronous generator of a fan based on the idea of the virtual synchronous generator is needed.
Disclosure of Invention
The invention aims to provide a method for transforming a virtual synchronous machine of a fan based on the idea of the virtual synchronous machine, thereby overcoming the defect of insufficient control of the virtual synchronous machine of the existing fan.
In order to achieve the purpose, the invention provides a method for transforming a virtual synchronous machine of a fan based on the idea of the virtual synchronous machine, which comprises the following steps:
analyzing the operating characteristics of various variable speed fans and judging whether the variable speed fans can be used for virtual synchronous machine reconstruction or not;
selecting a variable speed fan capable of transforming a virtual synchronous machine to perform strategy analysis, and setting virtual synchronous machine control according to an analysis result, wherein the virtual synchronous machine control comprises the following steps: the active power control, the virtual inertia control and the reactive power control of the wind turbine generator are set, so that the transformation of the virtual synchronous machine of the wind turbine is completed.
Preferably, the plurality of variable speed fans comprises: the wind driven generator set comprises a fixed-speed wind driven generator set, a double-fed wind driven generator and a direct-drive wind driven generator.
Preferably, the variable speed fan capable of virtual synchronous machine modification comprises: double-fed wind driven generator and direct-drive wind driven generator.
Preferably, the wind turbine active power control includes:
the fan is required to provide a complete primary frequency modulation function, and similar to a conventional synchronous unit, a power margin needs to be reserved for the wind turbine unit, so that the fan has a certain power standby, namely, the fan needs to be in load shedding operation.
Preferably, the fan load shedding frequency modulation is realized by adopting pitch angle control.
Preferably, the virtual inertia control of the fan comprises:
analyzing the mechanical energy of the inertia support function of the virtual synchronous machine, and setting according to an analysis result: setting an initial pitch angle to reserve standby power for the fan, simultaneously enabling virtual inertia additional control, and when a low-frequency event occurs in the wind power generation system, jointly acting load shedding frequency modulation and inertia frequency modulation, namely, overlapping an active power reference value increment output by the inertia frequency modulation with an original active power reference value of the fan to obtain a new fan active power control instruction.
Preferably, the virtual inertia control of the wind turbine further includes: when the wind power generation system is disturbed, the dynamic frequency of the wind power generation system is determined by the inertia response of the generator in the first few seconds of the frequency drop.
Preferably, the wind turbine reactive power control includes:
the virtual synchronous machine control does not involve the change of a reactive power control strategy, so that the reactive power control of the wind turbine generator is conventional control.
Preferably, simulation analysis is carried out according to the virtual synchronous machine control, the conclusion that the frequency response characteristic of the system is improved most obviously in a frequency modulation mode combining fan load shedding frequency modulation and virtual inertia frequency modulation is obtained, and the virtual synchronous machine transformation method of the fan based on the virtual synchronous machine thought is further optimized.
Compared with the prior art, the invention has the following beneficial effects:
the method for reconstructing the conventional wind turbine into the virtual synchronous machine of the fan provided by the invention judges whether the variable speed fan can reconstruct the virtual synchronous machine or not by analyzing the operating characteristics of various variable speed fans; selecting a variable speed fan capable of transforming a virtual synchronous machine to perform strategy analysis, and setting virtual synchronous machine control according to an analysis result, wherein the virtual synchronous machine control comprises the following steps: the active power control, the virtual inertia control and the reactive power control of the wind turbine generator are set, so that the transformation of the virtual synchronous machine of the wind turbine is completed.
The method for transforming the conventional wind turbine generator into the virtual synchronous machine of the fan provided by the invention completes three aspects of analysis of the characteristics of the variable speed fan, control of the virtual synchronous machine and grid-connected simulation analysis, obtains the conclusion that the frequency modulation mode combining fan load shedding frequency modulation and virtual inertia frequency modulation is most obvious in improvement of the system frequency response characteristics, and provides a new solution for a new energy-friendly grid-connected mode.
A conventional wind turbine generator is transformed into a virtual synchronous machine of a fan, and can respond to low-frequency and high-frequency events of a system. When the system frequency is reduced, the virtual synchronous machine increases the transmission power under the action of the virtual inertia frequency modulation and primary frequency modulation functions, so that the reduction of the system frequency can be inhibited. When the system frequency rises, the virtual synchronous machine can reduce the active power output and inhibit the system frequency from rising under the action of the primary frequency modulation function.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only one embodiment of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a flow chart of a method for modifying a virtual synchronous machine of a wind turbine based on the idea of the virtual synchronous machine;
FIG. 2 is a graph of a typical wind energy conversion factor;
FIG. 3 is a schematic view of a simulation model of a wind power generation system;
FIG. 4 is a schematic diagram of a fan inertia control model;
FIG. 5 is a schematic structural diagram of an exemplary reactive \ voltage control simulation system;
FIG. 6 is a voltage curve diagram of a manufacturer test of a reactive \ voltage control simulation example;
FIG. 7 is a graph of simulated voltage of reactive \ voltage control simulation example;
FIG. 8 is a graph of the reactive \ voltage control simulation example manufacturer test power;
FIG. 9 is a graph of reactive \ voltage control simulation example simulation power curve;
FIG. 10 is a plot of system frequency perturbation;
FIG. 11 is a graph of a wind turbine generator power response manufacturer test;
FIG. 12 is a graph of a wind turbine power response simulation;
FIG. 13 is an example grid frequency response curve for a wind turbine;
FIG. 14 is a graph of wind turbine electromagnetic power and mechanical power response;
FIG. 15 is a graph of a wind turbine pitch angle change;
FIG. 16 is a graph of wind turbine power response curves and wind turbine rotor speed.
Detailed Description
The technical solutions in the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the method for modifying a virtual synchronous machine of a wind turbine based on the idea of the virtual synchronous machine provided by the present invention includes the following steps:
and S1, analyzing the operating characteristics of various variable speed fans, and judging whether the variable speed fans can be modified by the virtual synchronous machine.
Currently, common wind turbines are generally classified into the following types: the wind driven generator set comprises a fixed-speed wind driven generator set, a double-fed wind driven generator and a direct-drive wind driven generator. The specific analysis of the operating characteristics of various variable speed fans is as follows:
a) a wind generating set with a fixed rotating speed belongs to a constant-speed constant-frequency set, a squirrel-cage asynchronous generator is usually adopted as the generator, reactive compensation is required to be added at the generator end, the speed regulation range is narrow, the efficiency is low, and the wind generating set belongs to an early fan and is gradually eliminated. Because the speed regulation range is narrow, the fixed-speed wind generating set is not suitable for the transformation of the virtual synchronous machine.
b) The double-fed wind generating set belongs to a variable speed constant frequency set, and the generator part adopts a general wound-rotor asynchronous motor structure. The back-to-back converter connected with the wind power generation system on the rotor side is a bidirectional power converter, the power converter comprises two independent control parts, the direct current sides are connected, the amplitude and the angle of the rotor voltage can be controlled through the control of the power converter, and then active power and reactive power are controlled. The control capability of the double-fed motor is greatly improved compared with that of the conventional fixed-speed fan due to the introduction of the power converter, and the performance of the double-fed fan is closely related to a control strategy of the converter. The current general converter control strategy is a vector control strategy based on stator flux linkage orientation or stator voltage orientation, and decoupling control of active power and reactive power of a double-fed motor can be achieved by controlling the voltage amplitude and phase angle of a rotor converter. Therefore, the double-fed wind generating set can operate at variable speed, and the speed regulation range is large, so the double-fed wind generating set can modify the control strategy to realize the transformation of the virtual synchronous machine, and the rotational inertia is released by control to increase the power.
c) The direct-drive wind generating set also belongs to a variable-speed constant-frequency set, a generator generally adopts a multi-pole permanent magnet synchronous motor, the generator is completely connected with a wind generating system through a converter, the synchronous motor is connected with a power grid through a frequency converter, and the frequency converter is used for controlling the speed of the generator and the active power exchanged with the power grid. The frequency converter comprises two back-to-back voltage source converters which are connected through a direct current capacitor. The frequency converter can enable the generator to control the terminal voltage and frequency of the generator according to the ideal optimized rotating speed of the wind turbine, and the terminal voltage and frequency of the generator are unrelated to the voltage and frequency of a power grid. Compared with a double-fed fan, the direct-drive fan has the advantages of: 1) the transmission system is greatly simplified, the system efficiency is improved, the mechanical noise and the maintenance amount are reduced, and the service life and the operation reliability of the unit are improved; 2) the generator is isolated from the power grid through the converter, the adaptability to the power grid fault is stronger, and low-voltage ride through is easier to realize. The direct-drive wind generating set and the double-fed wind generating set can modify a control strategy to realize the transformation of a virtual synchronous machine, and the rotational inertia is released by control to increase the power.
The wind energy utilization coefficient Cp of the variable speed wind turbine is related to the tip speed ratio lambda and the pitch angle theta of the wind turbine, and can be simplified and expressed as a nonlinear function of lambda and theta in dynamic simulation:
Figure BDA0003410475660000051
in the above formula, αijFor calculating the coefficient, it is generally obtained by fitting the measured values, and a specific typical wind energy conversion coefficient curve diagram is shown in fig. 2.
S2, selecting a variable speed fan capable of transforming the virtual synchronous machine to perform strategy analysis, and setting virtual synchronous machine control according to an analysis result, wherein the virtual synchronous machine control comprises: the active power control, the virtual inertia control and the reactive power control of the wind turbine generator are set, so that the transformation of the virtual synchronous machine of the wind turbine is completed. The method specifically comprises the following steps:
s21, selecting a variable speed fan capable of carrying out virtual synchronous machine transformation for strategy analysis, and respectively analyzing cooperative control based on an additional energy storage system, load shedding operation control based on reserved power reserve and virtual inertia control based on self rotary inertia, specifically:
and S211, cooperative control based on an additional energy storage system. The virtual synchronous wind power generation system depending on energy storage is cooperatively controlled by matching with the energy storage equipment, so that the external characteristics of the synchronous generator can be simulated by the characteristics of an interface after the fan and the energy storage equipment are output in parallel, the MPPT (maximum power point tracking) and current vector control modes of the fan in the scheme are kept unchanged, and the virtual synchronous characteristics of a grid-connected interface of the system are mainly realized by the configured additional energy storage equipment. The energy storage device is connected with the output end of the fan in parallel through the three-phase inverter and then fed into a power grid, the energy storage inverter adopts a traditional virtual synchronous inverter control mode, and only the sum of total active power and reactive power output by the fan and the energy storage equipment at a grid-connected interface is required to be used as a feedback power value required by the control of the virtual synchronous generator. Because this scheme need not to change the fan converter, its transformation cost to wind turbine generator system is lower. The scheme is easy to realize on the basis of the three-phase synchronous inverter, and is also suitable for virtual synchronization transformation schemes of other new energy sources such as photovoltaic power generation and the like. However, the additional energy storage not only increases the equipment cost of the wind farm, but also the control method does not effectively utilize the rotational kinetic energy stored by the wind turbine.
And S212, load shedding operation control based on reserved power standby. At present, various methods for realizing virtual synchronous control strategies of the fan by modifying an MPPT curve or utilizing variable pitch regulation and the like are available, and the wind energy utilization coefficient is reduced by changing the speed ratio and the pitch angle of the blade tip. The unit load shedding operation is realized by using a method of moving an operation point to the right in a low wind speed area, or extra capacity required by frequency modulation is provided through overspeed load shedding operation; the method combines overspeed load shedding and pitch angle increasing control, and independent overspeed control is carried out only by increasing the rotating speed of a generator in a low wind speed area so as to meet the load shedding requirement; the load shedding requirement is met by matching with variable pitch in the middle wind speed area; in a high wind speed area, the maximum power instruction and the rotating speed protection instruction limit, and the load shedding operation can be completed only by using variable pitch regulation. The method is used for realizing virtual synchronous machine control by providing power standby through load shedding operation, does not effectively utilize the rotational kinetic energy stored by the fan, and needs to operate under the load shedding operation condition for a long time to provide power standby.
And S213, virtual inertia control based on the self rotational inertia. The GE company of a fan manufacturer provides an additional control model named WindiNERTIATM, frequency deviation signals are introduced to generate power increment, the power increment is matched with a converter controller and a wind wheel controller, the rotor inertia is used for increasing output of a fan, and rated power of about 10% can be provided for a short time at maximum when a low-frequency event occurs. Because the fan has rotary inertia, can adopt inertia control to provide inertia frequency modulation, need not to subtract the operation of carrying, the virtual inertia control of fan is better with the compatibility of original MPPT control, and the fan need not the energy storage equipment cooperation and also can possess the frequency modulation characteristic similar with the synchronous machine. However, the inertia frequency modulation of the fan is different from the inertia frequency modulation of a conventional synchronous machine, is not a spontaneous response, and is generally called as virtual inertia control, and compared with the inertia frequency modulation of the conventional synchronous machine, the inertia frequency modulation of the fan has obvious defects, because the rotation speed is reduced due to the increased power, the wind energy utilization efficiency is also reduced, and the power of the fan needs to be reduced to improve the rotation speed, so that the problem of power notch is caused, the frequency response characteristic after the fault is influenced, and even the frequency falls for the second time. Some scholars also propose more complex control methods to reduce the frequency secondary drop degree, such as a segmented inertia control mode based on torque limitation, when the frequency drop time occurs, the power output is increased to the maximum value of the torque limitation, then the power output is reduced according to the rotation speed change until the mechanical power and the electromagnetic power reach a stable point of balance, then the power output is reduced to restore the rotation speed until the maximum wind energy tracking state is entered again, and the method has the advantage that the power change amplitude is smaller in the rotation speed restoration stage. However, the control is complex, the realization difficulty is high, and the stability can not meet the practical engineering requirement.
Therefore, on the basis of realizing a virtual inertia control model of WindiNERTIATM proposed by GE fan company, aiming at the problem of frequency secondary drop, the invention provides a combined virtual synchronous machine control strategy for carrying out virtual inertia control on the basis of load shedding operation.
Therefore, S22, a complete wind power generation system involves a plurality of modules, and a simulation model of the wind power generation system is shown in fig. 3, and virtual synchronous machine control is respectively controlled according to the analysis result, the virtual synchronous machine control includes: wind turbine generator system active power control, the virtual inertia control of fan and wind turbine generator system reactive power control set up, carry out a plurality of controls simultaneously and reform transform to the completion reforms transform the virtual synchronous machine of fan, it is specific:
s221, the wind turbine active power control comprises the following steps: the fan is required to provide a complete primary frequency modulation function, and similar to a conventional synchronous unit, a power margin needs to be reserved for the wind turbine unit, so that the fan has a certain power standby, namely, the fan needs to be in load shedding operation. There are generally two implementations: the invention controls the pitch angle of the wind wheel or the rotating speed of the fan, and the invention adopts pitch angle control to realize load shedding and frequency modulation. The primary frequency modulation function of the fan relates to the links of fan field station level control, pitch angle control, torque control and local control.
S222, the control of the virtual inertia of the fan comprises the following steps:
analyzing the inertia support function mechanical energy of the virtual synchronous machine: because the relative value of the system frequency change is not too large (the frequency change is 1.6 percent of the maximum relative value which does not cause low-frequency load shedding action), the synchronous machine releases or absorbs electromagnetic power expression due to the change of the kinetic energy of the rotor in the system frequency change process, namely the virtual synchronous machine needs simulated inertia support power Pe(t) the expression is simplified as:
Figure BDA0003410475660000081
in the above formula, TjIs the rotor inertia time constant, f0Is the nominal frequency, f (t) is the instantaneous frequency of the system, PNIs the rated power of the synchronous machine.
The virtual inertia control function of the fan is as follows: the wind turbine virtual synchronous machine technology can be understood as a rotational inertia control technology, a wind turbine generator set is provided with a wind wheel and rotor rotating equipment, the rotating equipment has certain rotational inertia during operation, partial rotational inertia is released by responding to the reduction of the system frequency, and power output can be temporarily improved. Different from a conventional generator set, the fan inertia control technology is a control means, the rotor speed and the grid frequency of the conventional generator set are directly coupled, the frequency fluctuation of a system can be automatically inhibited by means of the rotor rotational inertia, and a fan responds to the frequency fluctuation by controlling. At present, a widely-applied virtual inertia control model of the fan is not available, a model 'WindiNERTIATM' proposed by a GE company of a fan manufacturer is deployed and applied in the GE fan, and is relatively mature, and the control model proposed by the GE company is adopted for simulation analysis, such as the fan inertia control model shown in FIG. 4. The virtual inertia control of the fan responds to the frequency deviation of the power grid, and an active power reference value increment dPwi is output through a dead zone link, a filtering link, an amplifying link and a blocking link. The virtual inertia control needs to be matched with the control of a conventional fan wind wheel, and the strategy adopted by GE is to modify a torque control parameter after the virtual inertia of the fan acts, specifically to reduce Kp _ trq from 3.0 to 0.5, Ki _ trq from 0.6 to 0.05, and Tref from 0.05 to 4.0. The reduction of PI link parameters can weaken the response of Pref _ trq to the rotating speed deviation, and the superposition of an active power reference value increment dPwi can ensure that the fan can effectively increase the power, and can automatically reduce the power and recover the power
Therefore, according to the analysis results, settings are made: setting an initial pitch angle to reserve standby power for the fan, simultaneously enabling virtual inertia additional control, and when a low-frequency event occurs in the wind power generation system, jointly acting load shedding frequency modulation and inertia frequency modulation, namely superposing an active power reference value increment dPwi output by the inertia frequency modulation on an original active power reference value Pref _ trq of the fan to obtain a new fan active power control instruction Pref. When the wind power generation system is disturbed, such as the generator is disconnected from the network, the transient drop of the system frequency is often caused, and the dynamic frequency of the wind power generation system is determined by the inertia response of the generator in the first few seconds of the frequency drop.
S23, the wind turbine generator reactive power control comprises the following steps: the virtual synchronous machine control does not relate to the change of a reactive power control strategy and does not influence the original reactive power control of the fan. The fan unit reactive power control relates to the links of fan station level control and local control.
The traditional synchronous machine has some inherent inertia energy storage networks, and simultaneously, the traditional synchronous machine is matched with the action of a speed regulator, so that the functions of reducing the speed of initial frequency reduction and stabilizing the system frequency can be achieved. However, the existing wind turbine does not have inertia response, and for large-area low-frequency accidents, the wind turbine has inertia response capacity due to the virtual inertia characteristic. When the wind speed is higher than the rated wind speed, the active power output can be improved by retracting the propeller. When the wind speed is lower than the rated wind speed, the virtual synchronous machine is adopted for control, the rotating speed is reduced, the active output is improved, but the mechanical power of the fan is reduced due to the reduction of the rotating speed, so that only short-time power support can be provided, the active output needs to be reduced, the rotating speed is increased, otherwise, the fan stops rotating, the process that the wind wheel and the rotor release inertia of the fan is complex, and theoretical and simulation analysis needs to be carried out on the influence of the stability of a power grid through modeling.
S3, carrying out simulation analysis according to the virtual synchronous machine control to obtain a frequency modulation mode combining fan load shedding frequency modulation and virtual inertia frequency modulation:
a) reactive \ voltage control: the simulation algorithm is shown in fig. 5. Wherein generator Gen _1 represents an infinite system and Gen _2 represents a wind turbine. Different parallel impedances are connected in the calculation example, voltage mutation is realized, and the response of the wind turbine generator/wind power plant is observed. Different parallel impedances are connected in a single arithmetic example to realize voltage mutation and observe the response of the wind turbine generator/wind power plant, and the attached drawings of a manufacturer test curve and a simulation curve are shown in FIGS. 6-9. As can be seen from the simulation curve, the wind turbine generator has reactive power/voltage control capability, can respond to the voltage drop of the bus, and increase the reactive power output, and the simulation effect is also verified by comparing with the test curve of a manufacturer.
b) Active \ frequency control: primary frequency modulation control:
(1) the wind speed is greater than the rated wind speed: and simulating the frequency change of the system, and observing the active control quantity change of the wind turbine generator under the control of the virtual inertia. The fan is in a rated output state, the wind speed is higher than the rated wind speed, and the initial pitch angle is higher than 0. The system frequency perturbation curve is shown in fig. 10. As can be seen from the simulation results of fig. 11 and 12, when the wind speed is higher than the rated wind speed, the pitch angle of the wind turbine generator can be reduced by retracting the blades, and the active power exceeding the rated power by 10% is output. The frequency control is only used for transient frequency response and does not participate in steady-state frequency modulation, so that when the frequency change is relatively flat, the active power is gradually recovered to a rated value. Since the device has a long term overload capability of 10%, the support time is only related to the system frequency variation.
(2) Load shedding operation frequency modulation: the Active Power Control (APC) function of the wind generating set can be used for system frequency modulation and is a part of a wind farm management and control system. An example of a grid frequency response curve for a wind turbine is shown in fig. 13, where the values of a through D on the response curve are set to specific values to meet the primary grid frequency control requirements. And responding when the system frequency is disturbed, and controlling the active power to improve or reduce the output of the wind turbine generator, wherein the premise is that the wind turbine generator is not fully generated under the normal operation condition, and an active margin is reserved for frequency modulation, for example, only 90% of power is output. Thus, the power output can be increased when the system loses part of its power supply and can be decreased when the system loses part of its load. After active power control is adopted, the response curve of the wind turbine generator is shown in fig. 14 and 15 (the fan is set in a 90% output state, 10% of power is reserved for standby, and the initial pitch angle is about 3.56 °). The wind turbine generator responds to system frequency disturbance under active power control, and the output of the wind turbine generator is improved through propeller retracting, so that the wind power plant can emit more power when the system has power shortage.
Virtual inertia control: inertia support control is generally applied to the situation that when the wind speed is lower than or equal to the rated wind speed, and the system frequency is detected to be reduced, the control system generates an additional power instruction to enable the fan to send out more power. By adopting the fan inertia control, the rotating speeds of the wind wheel and the rotor are reduced, so that the wind wheel and the rotor are separated from the optimal operating point of the fan, the wind energy utilization coefficient is reduced, the mechanical power is further reduced, only short-time power support can be provided, and then the active power output (lower than the initial power) needs to be reduced to increase the rotating speed and restore the normal operating state, otherwise, the rotating speed is continuously reduced, and the fan stops rotating. After the inertia control is adopted, the response curve of the wind turbine generator is shown in fig. 16, and as can be seen from fig. 16, the inertia control of the wind turbine generator can only provide active support for a short time and then is in an operation state lower than the initial power output, so that the power recovery process may have a certain adverse effect on the system frequency recovery.
Generally speaking, when the wind speed exceeds the rated wind speed, the virtual synchronizer of the wind turbine generator set controls the power provided for the system to mainly come from the excess power brought by the oar collecting, and when the wind power is stable, long-time support can be provided, so that the virtual synchronizer is beneficial to supporting the system frequency. When the wind speed is lower than the rated wind speed, the excess power provided by the virtual synchronous machine function of the fan comes from the rotational kinetic energy of the blades, so the supporting time is limited, and the rotating speed needs to be recovered as soon as possible, so the power recovery process may have certain adverse effects on the frequency recovery of the system, such as reducing the lowest frequency, prolonging the frequency recovery time and the like. Therefore, due to the limited supporting time and the uncontrollable wind power, the power supporting capacity of the virtual synchronous machine of the wind turbine is limited, the virtual synchronous machine can only participate in the dynamic frequency adjustment of the system, the steady-state frequency of the system is not changed, and the power reverse drop phenomenon in the recovery process can possibly have negative effects on the system frequency.
The above disclosure is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or modifications within the technical scope of the present invention, and shall be covered by the scope of the present invention.

Claims (9)

1. A method for transforming a virtual synchronous machine of a fan based on the idea of the virtual synchronous machine is characterized by comprising the following steps:
analyzing the operating characteristics of various variable speed fans and judging whether the variable speed fans can be used for virtual synchronous machine reconstruction or not;
selecting a variable speed fan capable of transforming a virtual synchronous machine to perform strategy analysis, and setting virtual synchronous machine control according to an analysis result, wherein the virtual synchronous machine control comprises the following steps: the active power control, the virtual inertia control and the reactive power control of the wind turbine generator are set, so that the transformation of the virtual synchronous machine of the wind turbine is completed.
2. A method for transforming a virtual synchronous machine of a wind turbine according to the idea of the virtual synchronous machine, as claimed in claim 1, wherein the plurality of variable speed wind turbines include: the wind driven generator set comprises a fixed-speed wind driven generator set, a double-fed wind driven generator and a direct-drive wind driven generator.
3. A method for transforming a virtual synchronous machine of a wind turbine according to claim 1, wherein the variable speed wind turbine capable of transforming the virtual synchronous machine comprises: double-fed wind driven generator and direct-drive wind driven generator.
4. The virtual synchronous machine thought-based virtual synchronous machine transformation method for the wind turbine according to claim 1, wherein the wind turbine active power control comprises:
the fan is required to provide a complete primary frequency modulation function, and similar to a conventional synchronous unit, a power margin needs to be reserved for the wind turbine unit, so that the fan has a certain power standby, namely, the fan needs to be in load shedding operation.
5. The virtual synchronous machine concept-based virtual synchronous machine transformation method for the wind turbine according to claim 4, wherein the load shedding and frequency modulation of the wind turbine are realized by adopting pitch angle control.
6. The virtual synchronous machine concept-based virtual synchronous machine transformation method for the wind turbine according to claim 1, wherein the virtual inertia control of the wind turbine comprises:
analyzing the mechanical energy of the inertia support function of the virtual synchronous machine, and setting according to an analysis result: setting an initial pitch angle to reserve standby power for the fan, simultaneously enabling virtual inertia additional control, and when a low-frequency event occurs in the wind power generation system, jointly acting load shedding frequency modulation and inertia frequency modulation, namely, overlapping an active power reference value increment output by the inertia frequency modulation with an original active power reference value of the fan to obtain a new fan active power control instruction.
7. The virtual synchronous machine concept-based virtual synchronous machine transformation method for the wind turbine according to claim 1, wherein the virtual inertia control of the wind turbine further comprises: when the wind power generation system is disturbed, the dynamic frequency of the wind power generation system is determined by the inertia response of the generator in the first few seconds of the frequency drop.
8. The virtual synchronous machine thought-based wind turbine virtual synchronous machine transformation method according to claim 1, wherein the wind turbine reactive power control comprises:
the virtual synchronous machine control does not involve the change of a reactive power control strategy, so that the reactive power control of the wind turbine generator is conventional control.
9. The virtual synchronous machine thought-based virtual synchronous machine transformation method for the wind turbine according to claim 1, characterized in that simulation analysis is performed according to the virtual synchronous machine control, the conclusion that the frequency response characteristic of the system is improved most obviously in a frequency modulation mode combining wind turbine load shedding frequency modulation and virtual inertia frequency modulation is obtained, and the virtual synchronous machine thought-based virtual synchronous machine transformation method for the wind turbine is further optimized.
CN202111525940.9A 2021-12-14 2021-12-14 Method for transforming virtual synchronous machine of fan based on idea of virtual synchronous machine Pending CN114421533A (en)

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