CN118157240A - Offshore wind reservoir sectional type joint frequency modulation control method and system - Google Patents
Offshore wind reservoir sectional type joint frequency modulation control method and system Download PDFInfo
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Abstract
The invention discloses a method and a system for controlling sectional type joint frequency modulation of offshore wind reservoirs, comprising the following steps: acquiring the frequency variation of the power grid; when the power grid frequency variation is larger than the power grid frequency threshold and the real-time angular velocity of the DFIG rotor is larger than the minimum angular velocity of the DFIG rotor, obtaining first active power through a first control model of a frequency modulation stage, and controlling the DFIG side converter to obtain a first control result; obtaining the real-time angular acceleration of the DFIG rotor according to the real-time angular speed of the DFIG rotor in the first control result; when the DFIG real-time angular acceleration is smaller than the preset angular acceleration, determining an auxiliary frequency modulation condition of the energy storage equipment according to the SOC value of the energy storage equipment, and obtaining second active power through a second control model of the rotating speed recovery stage; and controlling the DFIG side converter according to the second active power to obtain a second control result. The invention realizes that the offshore wind storage system responds and adjusts the power grid frequency change more efficiently.
Description
Technical Field
The invention relates to the technical field of converter control, in particular to a sectional type combined frequency modulation control method and system for offshore wind reservoirs.
Background
Because the power electronic converter is used in the offshore power generation field grid-connected system, the inertia time constant and primary frequency modulation capacity of the power distribution network are reduced, and how to design an effective control strategy of an offshore wind turbine to improve the frequency stability of the power grid during grid connection becomes one of the problems to be solved.
The existing fan control method is summarized into control strategies such as overspeed load shedding power control, virtual inertia control and the like, and although the control strategies have advantages, the overspeed load shedding power control needs to be frequently regulated to enable the fan to work in a full-load state for a long time, so that economy is not facilitated; although the virtual inertia control can make the fan work in the MPPT control mode, the control parameters are difficult to set, and the control load is increased. Therefore, a more efficient grid frequency control method is needed.
Disclosure of Invention
The invention provides a sectional type combined frequency modulation control method and system for offshore wind reservoirs, which realize that an offshore wind reservoir system responds and adjusts the frequency change of a power grid more efficiently.
In order to solve the technical problems, the embodiment of the invention provides a sectional type combined frequency modulation control method for offshore wind reservoirs, which comprises the following steps:
Acquiring a power grid real-time frequency and a power grid rated frequency, and acquiring a power grid frequency variation according to the power grid real-time frequency and the power grid rated frequency;
when the power grid frequency variation is larger than a power grid frequency threshold and the real-time angular velocity of the DFIG rotor is larger than the minimum angular velocity of the DFIG rotor, obtaining first active power through a first control model of a frequency modulation stage, and controlling a DFIG side converter according to the first active power to obtain a first control result;
obtaining the real-time angular acceleration of the DFIG rotor according to the real-time angular velocity of the DFIG rotor in the first control result;
When the DFIG real-time angular acceleration is smaller than the preset angular acceleration, determining an auxiliary frequency modulation condition of the energy storage equipment according to the SOC value of the energy storage equipment, and obtaining second active power through a second control model of a rotating speed recovery stage by combining the auxiliary frequency modulation condition;
and controlling the DFIG side converter according to the second active power to obtain a second control result.
It can be appreciated that compared with the prior art, the method provided by the invention can collect the power grid frequency and the rotor angular velocity of the DFIG in real time, starts the offshore doubly-fed wind turbine generator (Doubly-Fed Induction Generator, DFIG) to regulate and control the first control model comprising the frequency modulation stage and the second control model of the rotating speed recovery stage in a segmented manner when the power grid frequency fluctuation is out of the stable range, sets special judgment conditions to judge the power grid frequency and the wind turbine working state at the moment, adopts different control models at different stages of the DFIG, and utilizes the energy storage equipment to carry out auxiliary regulation. Therefore, the offshore wind storage system can be assisted to timely cope with the change of the power grid frequency, so that response and adjustment can be made more accurately, and the frequency stability and operation safety of the offshore wind storage grid-connected system are realized.
Further, after the power grid frequency variation is obtained, the method further comprises:
when the power grid frequency variation is smaller than a power grid frequency threshold value, judging the magnitude relation between the SOC value of the energy storage equipment and a preset SOC value;
if the SOC value of the energy storage device is smaller than a preset SOC value, charging the energy storage device;
and if the SOC value of the energy storage equipment is larger than or equal to a preset SOC value, obtaining third active power through a third control model of a maximum power tracking control stage, and controlling the DFIG side converter according to the third active power.
It can be understood that when the power grid frequency variation is smaller than the power grid frequency threshold, the method provided by the invention indicates that the power grid frequency fluctuates in a stable range, and the DFIG adopts a maximum power point tracking control model, so that the power generation right of the offshore wind turbine can be ensured.
Further, the third active power is obtained through a third control model of the maximum power tracking control stage, and a specific calculation formula is as follows: Wherein P mod_FA is the third active power output by the DFIG from the time F to the time A; k p is the working coefficient of the maximum power tracking control model; omega r is the DFIG rotor real-time angular velocity.
Further, the specific calculation formula for charging the energy storage device is as follows: p bin＝kbinPb_max; wherein P bin is the energy storage real-time charging power; k bin is the sagging coefficient during energy storage and charging; p b_max is the energy storage allowed maximum output power.
Further, after the grid frequency variation is greater than the grid frequency threshold, the method further includes:
If the real-time angular velocity of the DFIG rotor is smaller than or equal to the minimum angular velocity of the DFIG rotor, judging the magnitude relation between the SOC value of the energy storage device and the preset SOC value;
When the SOC value of the energy storage equipment is smaller than a preset SOC value, frequency modulation is carried out through a first control model in a frequency modulation stage;
And when the SOC value of the energy storage device is larger than or equal to a preset SOC value, frequency modulation is carried out through the energy storage device.
It can be appreciated that when the real-time angular velocity of the DFIG rotor is smaller than or equal to the minimum angular velocity of the DFIG rotor, the method provided by the invention determines whether the energy storage equipment or the DFIG is used for frequency modulation, so that more efficient resource allocation can be realized, and frequency change can be dealt with more timely.
Further, the obtaining the first active power through the first control model of the frequency modulation stage specifically includes:
Judging the magnitude relation between the current time grid frequency and the last time grid frequency, and if the current time grid frequency is smaller than or equal to the last time grid frequency, switching on a first control unit in a first control model of the frequency modulation stage through a first controllable switch, wherein the first control unit specifically comprises:
Pmod_BC＝Pref+ΔP
Wherein P mod_BC is the first active power output from the operation of the DFIG from the time B to the time C; p ref is the active power reference value; Δp is DIFG electromagnetic power ramp-up value; omega r、ωmin and omega N are the real-time rotating speed, the minimum rotating speed and the rated rotating speed of the rotor of the DFIG, and P TN_lim is the torque power stability threshold value at the rated rotating speed;
if the current time power grid frequency is greater than the last time power grid frequency, a second control unit in a first control model of the frequency modulation stage is connected through a first controllable switch, wherein the second control unit specifically comprises:
Wherein P mod_CD is the first active power output by the DFIG from the time C to the time D; p C and P' C are respectively the active power values corresponding to the time point C and the time point C when the DFIG is operated; omega rC and omega rC′ are rotational speeds at which the DFIG is operating at times C and C', respectively.
Further, determining the auxiliary frequency modulation condition of the energy storage device according to the SOC value of the energy storage device specifically includes:
If the SOC value of the energy storage device is smaller than a preset SOC value, the energy storage device participates in auxiliary frequency modulation;
if the SOC value of the energy storage device is larger than or equal to the preset SOC value, the energy storage device does not participate in auxiliary frequency modulation.
It can be understood that the method provided by the invention judges whether the energy storage equipment assists in frequency modulation according to the SOC (state of charge) value of the energy storage equipment, and can further improve the efficiency of stable control of the power grid frequency.
Further, the obtaining the second active power through the second control model in the rotational speed recovery stage specifically includes:
and switching on a third control unit in the second control model of the rotating speed recovery stage through a time control switch, wherein the third control unit specifically comprises:
Pmod_DE＝PD-kDE(ωr-ωrD)
Wherein P mod_DE is the second active power output by the DFIG from the time D to the time E; p D is the active power value corresponding to the time when the DFIG runs to D; k DE is the reference slope; omega r is the real-time rotating speed of the DFIG rotor; omega rD is the rotor rotation speed corresponding to the time when the DFIG runs to D;
After the first preset time, a fourth control unit in the second control model of the rotating speed recovery stage is connected through a time control switch, wherein the fourth control unit specifically comprises:
Pmod_EF＝PD-Pd
Wherein P mod_EF is the second active power output by the DFIG from the E time to the F time; p D is the active power value corresponding to the time when the DFIG runs to D; p d is the active power drop value of DFIG from time D to time E.
Further, the energy storage device participates in auxiliary frequency modulation, specifically:
Wherein P bout is the energy storage real-time output power; p b_max is the energy storage allowed maximum output power; k bout is the active power attenuation slope when the energy storage gradually exits the action; t 0 is a first discharge time; t 1 is a second discharge time; t 2 is the third discharge time.
It can be understood that the method provided by the invention respectively models the two stages of discharging the energy storage device, and the energy storage device in the first stage rapidly provides active power support for the power grid according to the maximum power output; and in the second stage, after the discharge is carried out for a period of time, the energy storage device gradually exits the action.
Correspondingly, the embodiment of the invention provides a marine wind reservoir sectional type joint frequency modulation control system, which comprises the following components:
the power grid frequency acquisition module is used for acquiring the power grid real-time frequency and the power grid rated frequency, and acquiring the power grid frequency variation according to the power grid real-time frequency and the power grid rated frequency;
The frequency modulation stage control module is used for obtaining first active power through a first control model of the frequency modulation stage when the power grid frequency variation is larger than a power grid frequency threshold value and the real-time angular velocity of the DFIG rotor is larger than the minimum angular velocity of the DFIG rotor, and controlling the DFIG side converter according to the first active power to obtain a first control result;
the angular acceleration acquisition module is used for acquiring the real-time angular acceleration of the DFIG rotor according to the real-time angular velocity of the DFIG rotor in the first control result;
The control module of the rotational speed recovery stage is used for determining an auxiliary frequency modulation condition of the energy storage equipment according to the SOC value of the energy storage equipment when the real-time angular acceleration of the DFIG is smaller than the preset angular acceleration, and obtaining second active power through a second control model of the rotational speed recovery stage by combining the auxiliary frequency modulation condition;
And the control result acquisition module is used for controlling the DFIG side converter according to the second active power to obtain a second control result.
Compared with the prior art, the system provided by the invention can acquire the power grid frequency and the DFIG rotor angular speed in real time, starts the sectional regulation of the offshore doubly-fed wind turbine generator when the power grid frequency fluctuation is out of the stable range, comprises a first control model of a frequency modulation stage and a second control model of a rotating speed recovery stage, sets special judgment conditions to judge the power grid frequency and the wind turbine working state at the moment, adopts different control models of different stages of DFIGs, and utilizes energy storage equipment to carry out auxiliary regulation. Therefore, the offshore wind storage system can be assisted to timely cope with the change of the power grid frequency, so that response and adjustment can be made more accurately, and the frequency stability and operation safety of the offshore wind storage grid-connected system are realized.
Drawings
Fig. 1: the step flow chart of the offshore wind reservoir sectional type joint frequency modulation control method provided by the embodiment of the invention;
Fig. 2: the DFIG sectional active power reference value change curve of the offshore wind reservoir sectional type joint frequency modulation control method provided by the embodiment of the invention;
Fig. 3: the DFIG sectional frequency modulation control block diagram of the offshore wind reservoir sectional type joint frequency modulation control method provided by the embodiment of the invention;
Fig. 4: the energy storage auxiliary control flow chart of the offshore wind storage sectional type joint frequency modulation control method provided by the embodiment of the invention;
Fig. 5: the embodiment of the invention provides a structural schematic diagram of a sectional type combined frequency modulation control system for offshore wind reservoirs.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps of the process, and further implementations are included within the scope of the preferred embodiment of the present application in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present application.
In the description of this specification, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
The invention provides a sectional type offshore doubly-fed wind turbine (Doubly-Fed Induction Generator, DFIG) control method for energy storage cooperative control, which designs a sectional type control mode of an offshore wind turbine, adopts different control measures for the offshore wind turbine when the frequency of a power grid is stable and the frequency is changed, and simultaneously utilizes the charge and discharge functions of energy storage equipment to carry out auxiliary adjustment on the stable control of the frequency of the power grid so as to realize the optimal control effect of the frequency stability of the power grid.
Example 1
Referring to fig. 1, a flowchart of steps of a method for controlling sectional type joint frequency modulation of offshore wind reservoir according to an embodiment of the present invention includes steps S101-S105, and the steps are as follows.
S101: and acquiring the actual frequency and the rated frequency of the power grid, and obtaining the frequency variation of the power grid according to the actual frequency and the rated frequency of the power grid.
In this embodiment, the power grid frequency variation is obtained according to the power grid actual frequency and the power grid rated frequency, and a specific formula is as follows: i f-f N i= |Δf|; wherein f is the actual frequency of the power grid; f N is the rated frequency of the power grid; Δf is the grid frequency variation.
S102: when the power grid frequency variation is larger than a power grid frequency threshold and the real-time angular velocity of the DFIG rotor is larger than the minimum angular velocity of the DFIG rotor, obtaining first active power through a first control model of a frequency modulation stage, and controlling the DFIG side converter according to the first active power to obtain a first control result.
In this embodiment, when the power grid frequency variation |Δf| is smaller than or equal to the power grid frequency threshold f lim, which means that the power grid frequency fluctuates in a stable range, the magnitude relation between the SOC value of the energy storage device and the preset SOC value is determined; if the SOC value of the energy storage device is smaller than the preset SOC value, charging the energy storage device, wherein the specific calculation formula is as follows: p bin＝kbinPb_max; wherein P bin is the energy storage real-time charging power; k bin is the sagging coefficient during energy storage and charging; p b_max is the energy storage allowed maximum output power. If the SOC value of the energy storage device is greater than or equal to a preset SOC value, obtaining a third active power through a third control model of a maximum power tracking (Maximum Power Point Tracking, MPPT) control stage, and controlling the DFIG side converter according to the third active power, wherein a specific calculation formula is as follows: Wherein P mod_FA is the third active power output by the DFIG from the time F to the time A; k p is the working coefficient of the maximum power tracking control model; omega r is the DFIG rotor real-time angular velocity.
The third active power of the DFIG gradually increases with the third control model until the steady state before the failure occurs is returned.
As a preferable scheme, in order to ensure that the energy storage battery can continuously and healthily and stably work, the set SOC range is as follows: 10% p bN≤SOC≤90％PbN; wherein P bN is the rated power of the energy storage device.
In this embodiment, when the power grid frequency variation |Δf| is greater than the power grid frequency threshold f lim, it means that the power grid frequency exceeds the stable range, and the magnitude relation comparison is performed on the minimum angular velocity of the DFIG rotor after the real-time velocity of the DFIG rotor is obtained.
As a preferable scheme, when the real-time angular velocity of the DFIG rotor is smaller than or equal to the minimum angular velocity of the DFIG rotor, judging the magnitude relation between the SOC value of the energy storage device and the preset SOC value; when the SOC value of the energy storage equipment is smaller than a preset SOC value, frequency modulation is carried out through a first control model in a frequency modulation stage; and when the SOC value of the energy storage device is larger than or equal to a preset SOC value, frequency modulation is carried out through the energy storage device.
When the real-time angular velocity of the DFIG rotor is larger than the minimum angular velocity of the DFIG rotor, the magnitude relation between the power grid frequency at the current moment and the power grid frequency at the last moment is judged.
Specifically, if the current grid frequency is less than or equal to the last grid frequency, the first control unit in the first control model of the frequency modulation stage is turned on through the first controllable switch, see in detail the BC stage in fig. 2, under the control of the first control unit, the electromagnetic power of the DFIG rises by Δp, the rotor releases part of kinetic energy, the first active power becomes P mod_BC and remains for a period of time, the DFIG provides stable active power support for the system, and the first control unit specifically includes:
Pmod_BC＝Pref+Δp
wherein P mod_BC is the first active power output from the operation of the DFIG from the time B to the time C; p ref is the active power reference value; Δp is DIFG electromagnetic power ramp-up value; omega r、ωmin and omega N are the real-time rotational speed, the minimum rotational speed and the rated rotational speed of the rotor of the DFIG, and P TN_lim is the torque power stability threshold at the rated rotational speed.
Specifically, the electromagnetic power of the DFIG is always greater than the mechanical power in the frequency modulation stage, after the first active power is supported and output for a period of time, the rotor starts to release kinetic energy, if the current grid frequency is greater than the previous grid frequency, the current DFIG operation curve corresponds to the CD stage in fig. 2, the grid frequency rises, which also indicates that the DFIG rotor needs to release kinetic energy to maintain the requirement of rising of the grid frequency, and the second control unit in the first control model of the frequency modulation stage is turned on through the first controllable switch, where the second control unit specifically includes:
Wherein P mod_CD is the first active power output by the DFIG from the time C to the time D; p C and P' C are respectively the active power values corresponding to the time point C and the time point C when the DFIG is operated; omega rC and omega rC′ are rotational speeds at which the DFIG is operating at times C and C', respectively.
S103: and obtaining the real-time angular acceleration of the DFIG rotor according to the real-time angular velocity of the DFIG rotor in the first control result.
As a preferable scheme, deriving the real-time angular velocity of the DFIG rotor in the first control result to obtain the real-time angular acceleration of the DFIG rotor, and comparing the real-time angular acceleration of the DFIG rotor with a preset angular acceleration.
S104: and when the DFIG real-time angular acceleration is smaller than the preset angular acceleration, determining an auxiliary frequency modulation condition of the energy storage equipment according to the SOC value of the energy storage equipment, and combining the auxiliary frequency modulation condition, and obtaining second active power through a second control model of the rotating speed recovery stage.
In this embodiment, the energy storage device participates in auxiliary frequency modulation, specifically: at the time t 0 to t 1, the energy storage device rapidly acts to provide active power support for the power grid according to the maximum power output; after a period of time from discharge, at times t 1 to t 2, the energy storage device gradually exits the action:
Wherein P bout is the energy storage real-time output power; p b_max is the energy storage allowed maximum output power; k bout is the active power attenuation slope when the energy storage gradually exits the action; t 0 is a first discharge time; t 1 is a second discharge time; t 2 is the third discharge time.
Preferably, the preset angular acceleration is 0.0005, when the real-time angular acceleration of the DFIG is smaller than the preset angular acceleration, namelyAt this time, the DFIG frequency modulation phase is considered to be ended, and the rotational speed recovery phase is entered, and the DE phase in fig. 2 is described in detail.
Specifically, a third control unit in the second control model of the rotational speed recovery phase is turned on by a time-controlled switch, the third control unit specifically being:
Pmod_DE＝PD-kDE(ωr-ωrD)
Wherein P mod_DE is the second active power output by the DFIG from the time D to the time E; p D is the active power value corresponding to the time when the DFIG runs to D; k DE is the reference slope; omega r is the real-time rotating speed of the DFIG rotor; omega rD is the rotor speed corresponding to the time when the DFIG is operated to D.
Specifically, after a first preset time, a fourth control unit in the second control model of the rotational speed recovery stage is turned on through a time control switch, and the fourth control unit specifically includes:
Pmod_EF＝PD-Pd
Wherein P mod_EF is the second active power output by the DFIG from the E time to the F time; p D is the active power value corresponding to the time when the DFIG runs to D; p d is the active power drop value of DFIG from time D to time E.
As a preferred solution, the specific calculation formula of the first preset time t DE is: Wherein P d is the active power drop value of the DFIG from the time D to the time E; k DE is the reference slope.
S105: and controlling the DFIG side converter according to the second active power to obtain a second control result.
As a preferred scheme, please refer to fig. 3, which is a DFIG sectional frequency modulation control block diagram of a sectional type joint frequency modulation control method for offshore wind reservoir according to an embodiment of the present invention. The sectional frequency modulation control is divided into three parts, namely a frequency modulation stage, a rotating speed recovery stage and an MPPT control stage. The frequency modulation stage corresponds to the BC section and the CD section in the figure 2, the frequency modulation stage is built according to the first control unit and the second control unit, the judgment condition is that the current power grid frequency is in a magnitude relation with the power grid frequency at the last moment, and if the current power grid frequency is larger than the power grid frequency at the last moment, the first controllable switch is connected with the CD section; and if the current power grid frequency is smaller than or equal to the power grid frequency at the last moment, the first controllable switch is connected with the BC segment. The rotational speed recovery stage corresponds to the DE section and the EF section in the graph 2, is built according to a third control unit and a fourth control unit, judges whether a first preset time is elapsed or not, and if the first preset time is not elapsed, the time control switch is connected with the DE section; if the first preset time is elapsed, the time control switch is connected with the EF section. The output of the frequency modulation stage and the output of the rotating speed recovery stage are judged and output through the second controllable switch in advance, a judging bar is the magnitude relation between the real-time angular velocity of the DFIG rotor and the minimum angular velocity of the DFIG rotor, if the real-time angular velocity of the DFIG rotor is smaller than the minimum angular velocity of the DFIG rotor, the output of the second controllable switch and the MPPT control stage (corresponding to the FA section in fig. 2) are judged through the third controllable switch, the judging condition is the magnitude relation between the power grid frequency variation and the power grid frequency threshold, and if the power grid frequency variation is larger than the power grid frequency threshold, the third controllable switch is switched to the frequency modulation control stage through the MPPT control stage, so that the DFIG active power is finally output, and acts on the control of the DFIG side converter to regulate the power grid frequency to be stable.
As a preferred scheme, please refer to fig. 4, which is a flow chart of energy storage auxiliary control of a sectional type combined frequency modulation control method for offshore wind energy storage according to an embodiment of the present invention. Firstly, collecting the real-time frequency f of the power grid and the rotating speed omega r of the rotor of the offshore wind turbine, judging whether the frequency change quantity delta f of the power grid exceeds a limiting range, if not, indicating that the frequency of the power grid is stable, judging whether to charge the energy storage, and ending the flow. If so, continuously judging whether omega r is larger than a minimum value omega min, if omega r<ωmin, firstly mobilizing the stored energy to carry out frequency modulation, and if the stored energy SOC is within a protection value, continuously carrying out frequency modulation through the DFIG; if omega r>ωmin, the DFIG is directly used for frequency modulation, the frequency modulation stage and the rotating speed recovery stage of the DFIG are entered, whether the SOC of the stored energy is in a safety range or not is judged, if yes, the energy storage auxiliary is mobilized for frequency modulation, otherwise, the DFIG is independently used for frequency modulation, and the process is ended.
The method provided by the invention can collect the power grid frequency and the DFIG rotor angular velocity in real time, starts the offshore doubly-fed wind turbine generator (Doubly-Fed Induction Generator, DFIG) to regulate and control the first control model including the frequency modulation stage and the second control model including the rotating speed recovery stage in a segmented manner when the power grid frequency fluctuation is out of the stable range, sets special judgment conditions to judge the power grid frequency and the wind turbine working state at the moment, adopts different control models in different stages of DFIG, and utilizes energy storage equipment to carry out auxiliary regulation. Therefore, the offshore wind storage system can be assisted to timely cope with the change of the power grid frequency, so that response and adjustment can be made more accurately, and the frequency stability and operation safety of the offshore wind storage grid-connected system are realized.
Example two
Referring to fig. 5, a schematic structural diagram of a marine wind reservoir segmented joint fm control system according to an embodiment of the invention is shown, where the system includes: the system comprises a power grid frequency acquisition module 201, a frequency modulation stage control module 202, an angular acceleration acquisition module 203, a rotating speed recovery stage control module 204 and a control result acquisition module 205.
The power grid frequency acquisition module 201 is configured to acquire a power grid real-time frequency and a power grid rated frequency, and obtain a power grid frequency variation according to the power grid real-time frequency and the power grid rated frequency.
The frequency modulation stage control module 202 is configured to obtain a first active power through a first control model of a frequency modulation stage when the grid frequency variation is greater than a grid frequency threshold and the real-time angular velocity of the DFIG rotor is greater than a minimum angular velocity of the DFIG rotor, and control the DFIG side converter according to the first active power to obtain a first control result.
The angular acceleration obtaining module 203 is configured to obtain a real-time angular acceleration of the DFIG rotor according to the real-time angular velocity of the DFIG rotor in the first control result.
The rotational speed recovery stage control module 204 is configured to determine an auxiliary frequency modulation condition of the energy storage device according to the SOC value of the energy storage device when the DFIG real-time angular acceleration is less than the preset angular acceleration, and obtain a second active power through a second control model of the rotational speed recovery stage in combination with the auxiliary frequency modulation condition.
The control result obtaining module 205 is configured to control the DFIG side converter according to the second active power, and obtain a second control result.
In this embodiment, after the grid frequency obtaining module 201, the method further includes: the maximum power tracking control module is used for judging the magnitude relation between the SOC value of the energy storage device and a preset SOC value when the power grid frequency variation is smaller than a power grid frequency threshold value; if the SOC value of the energy storage device is smaller than the preset SOC value, charging the energy storage device, wherein the specific calculation formula is as follows: p bin＝kbinPb_max; wherein P bin is the energy storage real-time charging power; k bin is the sagging coefficient during energy storage and charging; p b_max is the energy storage allowed maximum output power. If the SOC value of the energy storage device is greater than or equal to a preset SOC value, obtaining a third active power through a third control model of a maximum power tracking control stage, and controlling the DFIG side converter according to the third active power, wherein a specific calculation formula is as follows: Wherein P mod_FA is the third active power output by the DFIG from the time F to the time A; k p is the working coefficient of the maximum power tracking control model; omega r is the DFIG rotor real-time angular velocity.
In this embodiment, the fm stage control module 202 further includes: the energy storage frequency modulation participation judging module is used for judging the magnitude relation between the SOC value of the energy storage device and the preset SOC value if the real-time angular speed of the DFIG rotor is smaller than or equal to the minimum angular speed of the DFIG rotor; when the SOC value of the energy storage equipment is smaller than a preset SOC value, frequency modulation is carried out through a first control model in a frequency modulation stage; and when the SOC value of the energy storage device is larger than or equal to a preset SOC value, frequency modulation is carried out through the energy storage device.
In this embodiment, the fm stage control module 202 specifically includes: the first control unit sub-module and the second control unit sub-module. The first control unit submodule is used for judging the magnitude relation between the current time power grid frequency and the last time power grid frequency, if the current time power grid frequency is smaller than or equal to the last time power grid frequency, the first control unit in the first control model of the frequency modulation stage is connected through a first controllable switch, and the first control unit specifically comprises: p mod_BC＝Pref +ΔP; Wherein P mod_BC is the first active power output from the operation of the DFIG from the time B to the time C; p ref is the active power reference value; Δp is DIFG electromagnetic power ramp-up value; omega r、ωmin and omega N are the real-time rotational speed, the minimum rotational speed and the rated rotational speed of the rotor of the DFIG, and P TN_lim is the torque power stability threshold at the rated rotational speed. The second control unit sub-module is configured to switch on, through a first controllable switch, a second control unit in a first control model of the frequency modulation stage if the current grid frequency is greater than the last grid frequency, where the second control unit is specifically: Wherein P mod_CD is the first active power output by the DFIG from the time C to the time D; p C and P' C are respectively the active power values corresponding to the time point C and the time point C when the DFIG is operated; omega rC and omega rC′ are rotational speeds at which the DFIG is operating at times C and C', respectively.
In this embodiment, the rotational speed recovery stage control module 204 specifically includes: a third control unit sub-module and a fourth control unit sub-module. The third control unit sub-module is configured to switch on a third control unit in the second control model of the rotational speed recovery stage through a time control switch, where the third control unit specifically is: p mod_DE＝PD-kDE(ωr-ωrD); wherein P mod_DE is the second active power output by the DFIG from the time D to the time E; p D is the active power value corresponding to the time when the DFIG runs to D; k DE is the reference slope; omega r is the real-time rotating speed of the DFIG rotor; omega rD is the rotor speed corresponding to the time when the DFIG is operated to D. The fourth control unit submodule is configured to switch on, after a first preset time, a fourth control unit in the second control model of the rotational speed recovery stage through a time control switch, where the fourth control unit specifically is: p mod_EF＝PD-Pd; wherein P mod_EF is the second active power output by the DFIG from the E time to the F time; p D is the active power value corresponding to the time when the DFIG runs to D; p d is the active power drop value of DFIG from time D to time E.
In this embodiment, determining, according to the SOC value of the energy storage device, an auxiliary frequency modulation condition of the energy storage device specifically includes: if the SOC value of the energy storage device is smaller than the preset SOC value, the energy storage device participates in auxiliary frequency modulation, specifically: Wherein P bout is the energy storage real-time output power; p b_max is the energy storage allowed maximum output power; k bout is the active power attenuation slope when the energy storage gradually exits the action; t 0 is a first discharge time; t 1 is a second discharge time; t 2 is the third discharge time. If the SOC value of the energy storage device is larger than or equal to the preset SOC value, the energy storage device does not participate in auxiliary frequency modulation.
The more detailed working principle and step flow of the present system can be, but are not limited to, see embodiment one.
The system provided by the invention can collect the power grid frequency and the rotor angular speed of the DFIG in real time, starts the sectional regulation and control of the offshore doubly-fed wind turbine generator set when the power grid frequency fluctuation is out of the stable range, comprises a first control model of a frequency modulation stage and a second control model of a rotating speed recovery stage, sets special judgment conditions to judge the power grid frequency and the wind turbine working state at the moment, adopts different control models of the DFIG at different stages, and utilizes energy storage equipment to carry out auxiliary regulation. Therefore, the offshore wind storage system can be assisted to timely cope with the change of the power grid frequency, so that response and adjustment can be made more accurately, and the frequency stability and operation safety of the offshore wind storage grid-connected system are realized.
The foregoing embodiments have been provided for the purpose of illustrating the general principles of the present invention, and are not to be construed as limiting the scope of the invention. It should be noted that any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art without departing from the spirit and principles of the present invention are intended to be included in the scope of the present invention.
Claims (10)
1. The marine wind reservoir sectional type joint frequency modulation control method is characterized by comprising the following steps of:
Acquiring a power grid real-time frequency and a power grid rated frequency, and acquiring a power grid frequency variation according to the power grid real-time frequency and the power grid rated frequency;
when the power grid frequency variation is larger than a power grid frequency threshold and the real-time angular velocity of the DFIG rotor is larger than the minimum angular velocity of the DFIG rotor, obtaining first active power through a first control model of a frequency modulation stage, and controlling a DFIG side converter according to the first active power to obtain a first control result;
obtaining the real-time angular acceleration of the DFIG rotor according to the real-time angular velocity of the DFIG rotor in the first control result;
When the DFIG real-time angular acceleration is smaller than the preset angular acceleration, determining an auxiliary frequency modulation condition of the energy storage equipment according to the SOC value of the energy storage equipment, and obtaining second active power through a second control model of a rotating speed recovery stage by combining the auxiliary frequency modulation condition;
and controlling the DFIG side converter according to the second active power to obtain a second control result.
2. The offshore wind reserve sectional type joint frequency modulation control method according to claim 1, wherein after obtaining the power grid frequency variation, further comprising:
when the power grid frequency variation is smaller than a power grid frequency threshold value, judging the magnitude relation between the SOC value of the energy storage equipment and a preset SOC value;
if the SOC value of the energy storage device is smaller than a preset SOC value, charging the energy storage device;
and if the SOC value of the energy storage equipment is larger than or equal to a preset SOC value, obtaining third active power through a third control model of a maximum power tracking control stage, and controlling the DFIG side converter according to the third active power.
3. The offshore wind reserve sectional type joint frequency modulation control method of claim 2, wherein the third active power is obtained through a third control model of a maximum power tracking control stage, and a specific calculation formula is as follows: Wherein P mod_FA is the third active power output by the DFIG from the time F to the time A; k p is the working coefficient of the maximum power tracking control model; omega r is the DFIG rotor real-time angular velocity.
4. The offshore wind reservoir segmented joint frequency modulation control method of claim 2, wherein the charging of the energy storage device comprises the following specific calculation formula: p bin＝kbinPb_max; wherein P bin is the energy storage real-time charging power; k bin is the sagging coefficient during energy storage and charging; p b_max is the energy storage allowed maximum output power.
5. The offshore wind reserve segmented joint frequency modulation control method of claim 1, further comprising, after the grid frequency variation is greater than a grid frequency threshold:
If the real-time angular velocity of the DFIG rotor is smaller than or equal to the minimum angular velocity of the DFIG rotor, judging the magnitude relation between the SOC value of the energy storage device and the preset SOC value;
When the SOC value of the energy storage equipment is smaller than a preset SOC value, frequency modulation is carried out through a first control model in a frequency modulation stage;
And when the SOC value of the energy storage device is larger than or equal to a preset SOC value, frequency modulation is carried out through the energy storage device.
6. The offshore wind reserve sectional joint frequency modulation control method of claim 1, wherein the obtaining the first active power through the first control model of the frequency modulation stage comprises:
Judging the magnitude relation between the current time grid frequency and the last time grid frequency, and if the current time grid frequency is smaller than or equal to the last time grid frequency, switching on a first control unit in a first control model of the frequency modulation stage through a first controllable switch, wherein the first control unit specifically comprises:
Pmod_BC＝Pref+ΔP
Wherein P mod_BC is the first active power output from the operation of the DFIG from the time B to the time C; p ref is the active power reference value; Δp is DIFG electromagnetic power ramp-up value; omega r、ωmin and omega N are the real-time rotating speed, the minimum rotating speed and the rated rotating speed of the rotor of the DFIG, and P TN_lim is the torque power stability threshold value at the rated rotating speed;
if the current time power grid frequency is greater than the last time power grid frequency, a second control unit in a first control model of the frequency modulation stage is connected through a first controllable switch, wherein the second control unit specifically comprises:
Wherein P mod_CD is the first active power output by the DFIG from the time C to the time D; p C and P' C are respectively the active power values corresponding to the time point C and the time point C when the DFIG is operated; omega rC and omega rC′ are rotational speeds at which the DFIG is operating at times C and C', respectively.
7. The offshore wind reservoir segmented joint frequency modulation control method of claim 1, wherein the determining the auxiliary frequency modulation condition of the energy storage device according to the SOC value of the energy storage device specifically comprises:
If the SOC value of the energy storage device is smaller than a preset SOC value, the energy storage device participates in auxiliary frequency modulation;
if the SOC value of the energy storage device is larger than or equal to the preset SOC value, the energy storage device does not participate in auxiliary frequency modulation.
8. The offshore wind reserve sectional type joint frequency modulation control method of claim 1, wherein the obtaining the second active power through the second control model of the rotational speed recovery stage specifically comprises:
and switching on a third control unit in the second control model of the rotating speed recovery stage through a time control switch, wherein the third control unit specifically comprises:
Pmod_DE＝PD-kDE(ωr-ωrD)
Wherein P mod_DE is the second active power output by the DFIG from the time D to the time E; p D is the active power value corresponding to the time when the DFIG runs to D; k DE is the reference slope; omega r is the real-time rotating speed of the DFIG rotor; omega rD is the rotor rotation speed corresponding to the time when the DFIG runs to D;
After the first preset time, a fourth control unit in the second control model of the rotating speed recovery stage is connected through a time control switch, wherein the fourth control unit specifically comprises:
Pmod_EF＝PD-Pd
Wherein P mod_EF is the second active power output by the DFIG from the E time to the F time; p D is the active power value corresponding to the time when the DFIG runs to D; p d is the active power drop value of DFIG from time D to time E.
9. The offshore wind reserve sectional type joint frequency modulation control method of claim 7, wherein the energy storage device participates in auxiliary frequency modulation, specifically:
Wherein P bout is the energy storage real-time output power; p b_max is the energy storage allowed maximum output power; k bout is the active power attenuation slope when the energy storage gradually exits the action; t 0 is a first discharge time; t 1 is a second discharge time; t 2 is the third discharge time.
10. An offshore wind reservoir segmented joint frequency modulation control system, comprising:
the power grid frequency acquisition module is used for acquiring the power grid real-time frequency and the power grid rated frequency, and acquiring the power grid frequency variation according to the power grid real-time frequency and the power grid rated frequency;
The frequency modulation stage control module is used for obtaining first active power through a first control model of the frequency modulation stage when the power grid frequency variation is larger than a power grid frequency threshold value and the real-time angular velocity of the DFIG rotor is larger than the minimum angular velocity of the DFIG rotor, and controlling the DFIG side converter according to the first active power to obtain a first control result;
the angular acceleration acquisition module is used for acquiring the real-time angular acceleration of the DFIG rotor according to the real-time angular velocity of the DFIG rotor in the first control result;
The control module of the rotational speed recovery stage is used for determining an auxiliary frequency modulation condition of the energy storage equipment according to the SOC value of the energy storage equipment when the real-time angular acceleration of the DFIG is smaller than the preset angular acceleration, and obtaining second active power through a second control model of the rotational speed recovery stage by combining the auxiliary frequency modulation condition;
And the control result acquisition module is used for controlling the DFIG side converter according to the second active power to obtain a second control result.
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