CN110611320B - Double-fed wind turbine generator inertia and primary frequency modulation method based on supercapacitor energy storage control - Google Patents
Double-fed wind turbine generator inertia and primary frequency modulation method based on supercapacitor energy storage control Download PDFInfo
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- CN110611320B CN110611320B CN201910659997.4A CN201910659997A CN110611320B CN 110611320 B CN110611320 B CN 110611320B CN 201910659997 A CN201910659997 A CN 201910659997A CN 110611320 B CN110611320 B CN 110611320B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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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
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
- H02J7/345—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering using capacitors as storage or buffering devices
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/76—Power conversion electric or electronic aspects
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E70/00—Other energy conversion or management systems reducing GHG emissions
- Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
Abstract
The invention discloses an inertia and primary frequency regulation strategy of a double-fed wind turbine generator controlled by energy storage of a super capacitor, which belongs to the technical field of new energy, wherein virtual inertia regulation and primary frequency regulation are realized by control of the super capacitor, so that improvement of the wind turbine generator is simplified, additional control of the wind turbine generator is not needed to be added, the super capacitor is connected with a direct current side bus capacitor of the double-fed wind turbine generator through a bidirectional DC/DC converter, and charge and discharge power of an energy storage device of the super capacitor directly flows to a load side through a grid side converter. The strategy ensures that the fan always operates in the tracking state of the maximum power point no matter the load is increased or reduced, thereby greatly improving the power generation benefit. If the load is reduced, controlling the super capacitor to charge, and absorbing redundant energy output by the fan; if the load is increased, the discharge of the super capacitor is controlled to meet the requirement of standby capacity supply during primary frequency modulation, so that the frequency modulation capacity is obviously improved.
Description
Technical Field
The invention belongs to the technical field of new energy, and particularly relates to a super capacitor energy storage-based doubly-fed wind turbine generator inertia and primary frequency modulation method suitable for carrying out primary frequency adjustment on a doubly-fed wind turbine generator under full working conditions.
Background
According to the published data of the international energy agency (International Energy Agency, IEA), the wind power proportion in the energy structure has been increased year by year since 2009, the average annual increase is 0.44%, the wind power generation accounts for 5.6% of the global energy demand in 2017, and the wind power permeability has a continuous trend. The frequency converter control strategy of the doubly-fed wind turbine can realize decoupling of active power and reactive power, and realizes the variable speed constant frequency function, thus being one of the mainstream types. The problem brought by the method is that the rotating speed of the DFIG rotor and the system frequency have no coupling relation, and the frequency modulation capability of the system is necessarily reduced when the wind power is connected in a large scale. In addition, the DFIG is usually in a maximum power point tracking (maximum power point tracking, MPPT) operation state, and no spare capacity is used for performing primary frequency adjustment, so that the problem of frequency stability of wind power grid connection is further aggravated.
Many researches are carried out at home and abroad on the frequency response of the wind turbine generator, and a plurality of mature control methods are provided to meet the construction requirements of the power grid friendly wind power plant. For example, virtual inertia control and droop control are overlapped on the basis of MPPT, so that equivalent inertia and damping of the system are effectively increased, but the droop control does not change mechanical power captured by the DFIG, so that the frequency dropping speed can be relieved to a certain extent, and secondary frequency dropping can be caused; if the DFIG is controlled to be in off-load operation in advance, a power margin can be reserved to enable the fan to continuously participate in frequency modulation. If the standby is directly obtained through pitch angle adjustment and participates in frequency modulation, but the mechanical adjustment precision is low, the speed is slow, and the general pitch angle is fixed and not adjusted in actual operation is considered, so that the safety, reliability and service life of a pitch control system are facilitated. The maximum power tracking curve is adjusted by the method, so that the fan operates on the suboptimal power curve to obtain certain spare capacity, but overspeed control reduces the rotating speed adjusting range under the disturbance of frequency rising and reduces the frequency adjusting capacity. And the two control modes do not consider the self-power generation benefit of the DFIG, so that the wind energy utilization rate is reduced. How to reasonably configure the regulation mechanism of the wind turbine to release the relation between the power generation benefit and the system stability is a problem to be solved at present.
On the other hand, the energy storage device is widely applied to wind power plants, and the existing method is to connect the battery and the super capacitor bank energy storage unit in parallel at the DC bus side of the back-to-back converter of the DFIG to stabilize the fluctuation of wind speed and smooth the power output; the DC bus is connected with the superconducting energy storage unit in parallel to improve the dynamic performance of the DFIG for coping with low-voltage events, and the possibility of the DFIG being provided with an energy storage device to participate in system frequency modulation is provided.
Disclosure of Invention
In combination with the problems, the primary frequency regulation strategy of the double-fed wind turbine generator needs to be improved, the economy of the DFIG operation and the system frequency stability are considered, and the inertia and primary frequency regulation strategy of the double-fed wind turbine generator based on the energy storage control of the super capacitor are provided. The strategy is improved on the basis of a maximum power tracking mode, when the load is reduced, the super capacitor is controlled to charge, redundant electric energy emitted by the doubly-fed wind turbine generator is absorbed, the increase of frequency is restrained, and the frequency adjusting capability is improved; when the system load increases, the energy storage device provides spare capacity for the wind turbine generator to participate in system frequency modulation, so that the system has primary frequency adjustment capability under all working conditions on the basis of realizing that the DFIG does not lose the power generation benefit; the frequency adjustment capability superior to that of the traditional overspeed load shedding control can be achieved without pitch angle adjustment under the random fluctuation scene of the source load, and the power generation benefit is obviously improved.
In order to prevent overcharge or overdischarge, it is necessary to first determine whether the current SOC state of the supercapacitor energy storage system satisfies SOC min ≤SOC(t)≤SOC max Constraint conditions. After the SOC constraint is met, the disturbance type is judged according to the load prediction module, the super-capacitor energy storage system starts to charge and discharge under the sagging control, and the output power reference value is P ref_scss ＝K scss Δf，K scss Is the sagging coefficient of the super capacitor energy storage system. When the system frequency is reduced, the super-capacitor energy storage system continuously discharges, and when the frequency is increased, the wind turbine generator system charges the super-capacitor energy storage system, so that the power output is reduced.
Drawings
Fig. 1 is a schematic block diagram of supercapacitor control under load disturbance.
Fig. 2 is a control strategy flow diagram of the supercapacitor energy storage system.
Fig. 3 is a schematic diagram of DFIG energy storage configuration.
Fig. 4 is a schematic diagram of constant power charge and discharge of the supercapacitor.
FIG. 5 is a graph showing efficiency of a super capacitor energy storage device
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings. Fig. 1 is a schematic block diagram of supercapacitor control under load disturbance, namely, energy storage control and virtual inertia control of the supercapacitor are added on the basis of maximum power tracking control. By adding the virtual inertia, the system response speed is high, and the transient stability of the system frequency is improved. The energy storage of the super capacitor participates in frequency modulation control, so that the frequency adjustment capability can be improved. The virtual inertia adjustment and the primary frequency adjustment are controlled by the super capacitor.
FIG. 2 is a control schematic block diagram of a supercapacitor energy storage system, first determining whether the current SOC of the supercapacitor energy storage system meets the SOC min ≤SOC(t)≤SOC max Constraint conditions. After the SOC constraint is met, the super capacitor energy storage system starts to charge and discharge under the sagging control, and the output power reference value is P ref_scss ＝K scss Δf. When the system frequency is reduced, the super-capacitor energy storage system continuously discharges, and when the frequency is increased, the wind turbine generator system charges the super-capacitor energy storage system, so that the power output is reduced.
Fig. 3 is a schematic diagram of a primary frequency modulation configuration scheme of a system in which the super capacitor energy storage device participates, and the super capacitor is connected with a direct-current side bus capacitor of the doubly-fed wind turbine through a bidirectional DC/DC converter. The rotor side and the grid side converter of the doubly-fed wind turbine generator can maintain an original control mode, and the grid side converter has the function of maintaining the voltage stability of the direct current bus capacitor, so that the charge and discharge power of the super-capacitor energy storage device directly flows to the load side through the grid side converter.
The capacity configuration of the energy storage unit needs to meet the primary frequency adjustment requirement under sudden load increase or sudden decrease disturbance, and if the capacity of the energy storage device is too small, sufficient spare capacity cannot be provided to participate in frequency adjustment; if the capacity of the energy storage device is too large, the cost of the energy storage system is increased, and a certain amount of capacity is wasted. Therefore, the capacity of the energy storage device needs to be reasonably set by combining the above factors.
The super capacitor energy storage device is in a constant power charge-discharge mode, and is shown in a charge-discharge schematic diagram in fig. 4 (a) and (b). Wherein the charging power is P c The discharge power is P d The voltage across the capacitor is U c The voltage at two ends of the super capacitor energy storage device is U, the charge and discharge depth is d=1-gamma, and gamma=U min /U max The minimum working voltage of the super capacitor is U as the voltage ratio min The highest working voltage is U max . As shown in fig. 4, the voltages at two ends of the super capacitor are as follows:
substituting the capacitance-current equation to obtain: />
Therefore, the charging power of the super capacitor can be obtained as follows: />
At time T c In, the voltage at two ends of the super capacitor is equal to the voltage U min Rising to the highest voltage U max The electric energy charged by the super capacitor energy storage device in the whole charging process can be obtained as follows: />
The actual electric energy charged into the energy storage device is +>
Therefore, the efficiency of the super capacitor energy storage device in the constant power charging mode is shown as follows: />
Similarly, at time T d In, the voltage of the super capacitor energy storage device is higher than the highest voltage U max To U (U) min The discharge energy is: />
The electric energy released by the energy storage device is as follows: />
The discharge efficiency of the integrated discharge lamp is as follows: />
In summary, the charging and discharging efficiency of the super capacitor energy storage device proposed herein can be obtained as follows: />
In order to maximize the efficiency of the super capacitor energy storage device, the super capacitor module voltage should be relatively large, and the voltage of a single capacitor (The Super Capacitor, abbreviated as SC) is usually not high, about 2.5V, so that the high-voltage large capacitor module can be formed by a plurality of SCs connected in series and in parallel to meet the requirement of high-power energy storage. If the energy storage device is formed by connecting m groups of super capacitor modules in series and connecting n groups of super capacitor modules in parallel, the maximum value of the output power of the energy storage device is as follows according to the maximum power output theorem: />
And should ensure that the power state output by the supercapacitor when it reaches the minimum voltage is the equation for full power output: />
The energy storage device efficiency curve shown in fig. 5 can be obtained. />
Claims (4)
1. The utility model provides a double-fed wind turbine generator system inertia and primary frequency modulation method based on super capacitor energy storage control under full operating mode, characterized by that is connected super capacitor with double-fed wind turbine generator system's direct current side busbar capacitance through two-way DC/DC converter, super capacitor energy storage controller detects the electric wire netting frequency, absorbs or releases electric energy from direct current busbar through two-way energy storage converter control super capacitor, rotor side and net side converter can maintain original control mode, net side converter maintains direct current busbar capacitance voltage's stability, the automatic exchange of direct current side and alternating current side electric energy or power is accomplished through net side converter to the charge-discharge power that the sagging control of super capacitor energy storage device.
2. The double-fed wind turbine generator inertia and primary frequency modulation method based on super capacitor energy storage control under the full working condition of claim 1 is characterized in that the action time of super capacitor energy storage is consistent with the action time of wind turbine generator to start overload or load shedding operation; if the load is increased, the backup capacity required by primary frequency modulation can be transmitted to the power grid side by controlling the discharge of the super capacitor; if the load is reduced, the power on the power grid side is absorbed by controlling the charging of the super capacitor, so that the doubly-fed wind turbine generator is always in a maximum power tracking mode, and the power generation benefit is maximized.
3. The double-fed wind turbine generator inertia and primary frequency modulation method based on super capacitor energy storage control under the full working condition of claim 1 is characterized in that the cost and the charge and discharge efficiency of the super capacitor bank are comprehensively considered, and the capacity of an energy storage unit of the super capacitor bank is optimally configured; the super capacitor adopts a constant power discharging mode, the charging and discharging efficiency is in direct proportion to the highest working voltage, the power state output by the super capacitor is still full power output when the maximum power output reaches the minimum voltage, and the high-voltage large-capacitance module is formed by a plurality of SCs in series and parallel to meet the high-power energy storage requirement.
4. The double-fed wind turbine generator inertia and primary frequency modulation method based on super capacitor energy storage control under the full working condition according to claim 1 is characterized in that virtual inertia adjustment and primary frequency adjustment are realized by super capacitor control, so that improvement of the wind turbine generator becomes simple and easy, additional control of the wind turbine generator is not needed, and the expansion function of the super capacitor is realized.
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| CN112636374B (en) * | 2021-03-09 | 2021-05-14 | 沈阳微控新能源技术有限公司 | Primary frequency modulation and virtual inertia response control method and device for wind power station |
| CN113595154A (en) * | 2021-07-22 | 2021-11-02 | 明阳智慧能源集团股份公司 | Wind turbine generator system power grid inertia frequency modulation method and system |
| CN113972668B (en) * | 2021-10-22 | 2024-03-12 | 国网安徽省电力有限公司电力科学研究院 | Wind-storage-combination-based electromagnetic transient control method for power system |
| CN115912397B (en) * | 2022-11-21 | 2024-03-15 | 华清安泰能源股份有限公司 | Frequency modulation control method, system and equipment for wind-storage-coordinated double-fed wind turbine generator |
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| CN105633983A (en) * | 2016-03-01 | 2016-06-01 | 国网甘肃省电力公司 | Control system for improving frequency support capability of wind turbine generator set by super capacitor |
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| CN105633983A (en) * | 2016-03-01 | 2016-06-01 | 国网甘肃省电力公司 | Control system for improving frequency support capability of wind turbine generator set by super capacitor |
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