CN114744747A - Control and optimization method and system for black start of wind storage system - Google Patents

Control and optimization method and system for black start of wind storage system Download PDF

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Publication number
CN114744747A
CN114744747A CN202210262419.9A CN202210262419A CN114744747A CN 114744747 A CN114744747 A CN 114744747A CN 202210262419 A CN202210262419 A CN 202210262419A CN 114744747 A CN114744747 A CN 114744747A
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wind
power
voltage
energy storage
grid
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柳丹
冀肖彤
江克证
康逸群
梅欣
邓万婷
熊平
肖繁
叶畅
胡畔
曹侃
谭道军
王伟
陈孝明
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State Grid Hubei Electric Power Co Ltd
Electric Power Research Institute of State Grid Hubei Electric Power Co Ltd
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State Grid Hubei Electric Power Co Ltd
Electric Power Research Institute of State Grid Hubei Electric Power 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
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H02J9/08—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems requiring starting of a prime-mover
    • 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
    • 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
    • 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
    • H02J3/381—Dispersed generators
    • 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
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • 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
    • 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

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Abstract

The invention discloses a control and optimization method for black start of a wind storage system, belongs to the technical field of electrical engineering, and comprises DFIG vector control of a bottom double-fed asynchronous wind driven generator and ESS double-closed-loop control of an energy storage system. The bottom layer control ensures the normal operation of the fan and the energy storage system, the upper layer control distributes the power of each energy storage system, and the energy storage system can distribute the power output according to different capacities based on the droop control; meanwhile, the method for optimizing the starting sequence of the electric fields is matched with the no-load grid-connected technology of the draught fan, and the impact of the wind power plants on the energy storage power station during the black start period can be reduced as much as possible, so that the method can effectively start each wind power plant to form a stable wind storage isolated network system, and ensure that the fluctuation of the bus voltage and the frequency is within the allowable range.

Description

Control and optimization method and system for black start of wind storage system
Technical Field
The invention belongs to the field of new energy power grid control, and particularly relates to a control and optimization method and system for black start of a wind storage system.
Background
Wind farms are important components of new power systems. In a traditional power system, a thermal power generating unit with self-starting capability is relied on, and electric energy supply can be recovered without external assistance after the system is in failure and is stopped, so that black start is realized. The wind turbine generator set does not have self-starting capability, a micro-grid formed by high-proportion wind power comprises a large number of power electronic devices, the inertia is small, the overload capacity is poor, the situation is greatly different from the situation that a rotary power supply is mainly used in a traditional power system, and the conventional black-start strategy of the traditional power system which is mature at present cannot be directly applied to the micro-grid system. Secondly, the micro-grid system is relatively fragile due to the fact that the micro-grid system comprises renewable energy sources with large volatility and randomness, such as photovoltaic energy, wind turbines and the like, and voltage and frequency instability is easily caused in the black start process. The introduction of an energy storage system will make it possible to use the wind farm as a black start power supply. When the power grid normally operates, the energy storage can improve the system stability; after the power grid has a blackout, the application of the energy storage technology can accelerate the recovery of the power supply of the power grid, for example, in the recovery process of the british blackout, the british power grid reduces the loss of the blackout by starting the energy storage power station.
At present, the research on black start by taking wind power/photovoltaic as a main network is just started, and the research is not put into practical engineering application. In the prior art, most wind storage system black start technologies aim to start thermal power generating units to recover power supply by taking the wind storage system as a black start power supply, rather than forming a stable microgrid by only depending on the wind storage system and local loads. Both differ greatly in time scale and stability during start-up. Meanwhile, the problems of excitation inrush current, fan starting and wind storage system stability in the black start process still need to be solved, and the processing modes of the problems are different under the condition that the traditional rotating power supply is not provided. Wind power plants researched in the prior art are generally distributed in a centralized manner, the influence of spatial distribution of the wind power plants on black start is rarely considered, and the performance of the black start can be improved by optimizing the starting sequence of each wind power plant actually. Therefore, it is necessary to combine and consider the characteristics of the microgrid to perform a deeper analysis on the black start problem of the microgrid.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a control and optimization method and a system for black start of a wind storage system, which are suitable for a micro-grid containing high-proportion wind power and can quickly start a wind power plant to recover power supply to a load when the micro-grid system is powered off accidentally.
In order to achieve the above object, the present invention provides a control method for a black start process of a wind storage system, comprising the following steps:
(1) each energy storage power station adopts a droop control strategy and is started to rated voltage U in a zero boost modenEstablishing stable frequency and voltage for the system, and simultaneously charging a no-load line and a transformer in the system;
(2) the wind power plant auxiliary equipment is put into, and the double-fed asynchronous wind driven generator has external voltage U in the step (1)nCarries out rotor grid connection under the support of the double-fed asynchronous wind driven generator and carries out rotor current i on the double-fed asynchronous wind driven generatorrd、irqControl is performed so that no-load electromotive force E of the stator winding0And bus voltage UnThe voltage tracking is carried out to realize the smooth grid connection of the subsequent fan;
(3) the stator of the double-fed asynchronous wind driven generator is connected to the grid, the rotor-side converter is switched from the hollow load grid-connected mode to the MPPT control mode in the step (2) to capture the maximum wind energy, and the stator-side converter stabilizes the direct-current side capacitor voltage UCAnd reactive power Q of grid connectionwindEnabling the wind power plant to finish self-starting and output with constant power;
(4) after the wind power plant finishes self-starting, putting corresponding loads into the wind power plant to form a stable wind power storage island system for supplying power to local loads;
(5) establishing a mathematical model of a power supply network to be researched, and calculating the equivalent electrical distance from each wind power plant to an energy storage power station for optimizing the black start sequence of each wind power plant;
(6) and (5) sequentially executing the steps (2) - (4) to each wind power plant according to the black start sequence determined in the step (5) to finish the black start process.
Further, the droop control in the step (1) is used for simulating the primary frequency modulation process of the traditional synchronous generator, the reactive power and the active power output by the inverter are adjusted according to the system voltage and frequency variation, and the voltage and frequency adjustment process is realized through the following objective equation:
Pref＝Pe-Dp(ωn-ω)
Qref＝Qe-Dq(Un-U)
obtaining a power instruction through the error of voltage and frequency, and obtaining an internal potential reference value of the energy storage system through a voltage-current double closed loop, wherein Pref、QrefTo set active and reactive reference values, Pe、QeIs the actual output power of the inverter; omeganOmega is the rated frequency and the actual frequency of the system, UnU is the rated output voltage and the actual output voltage, Dp、DqP-omega and Q-V droop coefficients;
linearly increasing the output voltage command of the inverter from 0 to the rated system voltage UnAnd excitation inrush current generated when the no-load transformer is switched on is restrained, and the follow-up self-starting failure of the wind power plant caused by the excitation inrush current is prevented.
Further, in the step (2), the no-load electromotive force of the stator winding is expressed by the rotor current as:
Figure BDA0003550571530000031
wherein L ismIs equivalent mutual inductance of stator and rotor windings, uds、uqsDq components of the stator winding voltage, respectively, if oriented in the stator voltage vector, should have uds＝Us，uqs＝0；iqr、idrIs a rotor current dq component, omega in the same coordinate system1For the synchronous rotating speed of the motor, a derivative term in the following steady state formula is 0, and a current instruction of a rotor winding obtained by combining the grid-connected requirement on the stator potential is as follows:
Figure BDA0003550571530000032
in the formula of UsCurrent error obtained for rated voltage of power networkAnd obtaining a voltage instruction of the rotor-side converter through a voltage loop PI regulator, thereby executing no-load starting of the double-fed asynchronous wind driven generator.
Further, the MPPT control mode in step (3) is specifically:
method for controlling mechanical power P of fan by adopting power feedback methodmechOptimum power-speed curve P for running in fanoptOn (omega), the control object is the stator output active power P1；
The transmission mechanism is approximately regarded as a rigid body, and the power of the system is balanced in a steady state:
Pmech-ωTf＝P1+PCu+PFe
in the formula: p1Outputting active power for the DFIG stator; j and TfRespectively an inertia time constant and a friction torque of the transmission mechanism; pFeAnd PCuThe iron loss and the stator and rotor copper loss of the doubly-fed asynchronous wind driven generator are respectively; continuously changing fan stator power instruction P in a certain wind speed range* 1(ω) to PmechAccording to PoptAnd (omega) is regularly changed, and maximum power tracking is realized.
Further, in the step (5), a mathematical model of the power supply network to be researched is established, and the starting sequence of the wind power plant is optimized by using the electrical distance, which specifically comprises the following steps:
transforming an impedance network in the system into a network with only direct impedance between the wind power plant and the energy storage power station, and determining an n-order node impedance matrix Z of the systemnetI.e. the nodal admittance matrix YnetWherein n is the number of nodes of the network; each electrical element in the network is equivalent with the following model:
reactance X for transformerTEquivalently, neglecting its excitation branch Rm+jXmAnd a winding resistance R;
impedance Z for power transmission lineLEquivalence, neglecting the capacitance to ground;
the energy storage power station adopts a v-f control strategy, an infinite voltage source is used for connecting an equivalent reactance model in series for equivalence, and in a per unit value system, the potential E of the equivalent voltage source is equivalent to the potential EesiAnd resistanceResistance to xesiRespectively expressed as:
Eesi＝1
Figure BDA0003550571530000041
wherein SBIs the capacity base value of the system, SesiThe capacity of the energy storage power station connected to the node i;
a P-Q control strategy is adopted in the wind power plant, when the voltage of a power grid is assumed to be constant, an infinite current source is used for connecting an equivalent reactance model in parallel for equivalence, and the equivalent impedance is expressed as follows:
Figure BDA0003550571530000042
wherein SwiIs the wind farm capacity connected to node i.
Further, the step (5) of calculating the equivalent electrical distance from each wind farm to the energy storage power station specifically comprises:
calculating the transfer impedance between the wind power plant at the node i and the energy storage power station, wherein the specific calculation formula is as follows:
Figure BDA0003550571530000051
wherein A is a set of node numbers connected with the energy storage, and Zi,jNode impedance matrix Z representing the entire networknetElement of ith row and jth column, xesjRepresenting the equivalent impedance of the jth energy storage power station;
calculating the voltage of the wind power plant grid-connected node at the node i according to the transfer impedance, namely the equivalent electrical distance, wherein the specific calculation formula is as follows:
Figure BDA0003550571530000052
wherein EesiFor equivalent potential, x, of the ith energy-storage stationwiIs as followsEquivalent impedance of i wind farm, ZwiTransfer impedance calculated for the above formula, grid-connected node voltage U of wind farmwiThe larger the power is, the stronger the reactive power supply capacity of the energy storage power station to the wind turbine is, the closer the reactive power electrical distance from the energy storage power station to the wind power plant is, the earlier the wind power plant is started in the black starting process, and therefore the starting sequence of each wind power plant is determined.
Further, the wind storage system comprises a rotor-side converter and a grid-side converter, wherein,
the rotor-side converter realizes decoupling control of active power and reactive power of a stator of the double-fed asynchronous wind driven generator through stator flux linkage directional vector control;
the grid-side converter realizes decoupling control of the active power output by the grid side of the double-fed asynchronous wind driven generator and the reactive power of a grid-side converter loop through grid voltage directional vector control.
A control and optimization system for black start of a wind storage system, comprising: a computer-readable storage medium and a processor;
the computer-readable storage medium is used for storing executable instructions;
the processor is used for reading executable instructions stored in the computer-readable storage medium and executing the control and optimization method for the black start of the wind storage system.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
(1) the invention simulates the grid connection process of the synchronous generator by considering the impact of the wind power station incorporated into the power grid to the energy storage power station instantly. Before the DFIG outputs power outwards, the output current of the converter on the rotor side is controlled, the tracking of the no-load potential of the stator on the voltage of a power grid is realized, and therefore the circulation between a fan and stored energy is avoided. And after the wind power plant completes grid connection, the rotor side converter is switched to MPPT control under a stable state, and maximum power tracking is realized. According to the scheme, on the premise of not introducing other compensation equipment, the impact on the system generated by the wind turbine during grid connection can be reduced to the greatest extent, the transient response of power in the starting process is optimized, and the stability of the wind storage system is effectively kept;
(2) the invention provides a method for determining the starting sequence of each wind power plant in the black starting process by utilizing the concept of electrical distance, and for a general wind power-energy storage network, a node impedance matrix of the network can be established to solve the transfer impedance from each wind power plant to all energy storage power stations, so that the voltage U of a grid-connected node of the wind power plant is calculatedwiAnd the method is used for measuring the power supply capacity of the energy storage power station to the wind power plant at the point: the shorter the electrical distance, the more advantageous the start-up of the wind farm. The scheme is wide in application range and simple in operation, does not need to perform partitioning and complex operation on each unit, and can effectively optimize the transient process of black start by matching with the scheme in the step (1).
Drawings
Fig. 1 is a schematic flow chart of an embodiment of a wind storage microgrid black-start control method according to the present invention;
FIG. 2 is a schematic diagram of a topological structure of a distributed wind storage isolated network system provided by an embodiment of the invention;
FIG. 3 is an equivalent model of a distributed wind storage network provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of a vector control strategy of a doubly-fed wind generator provided by an embodiment of the invention;
FIG. 5 is a schematic diagram of an energy storage system topology provided by an embodiment of the invention;
FIG. 6 is a schematic diagram of an energy storage system control method provided by an embodiment of the invention;
fig. 7 and fig. 8 are simulation diagrams of output power of the energy storage device when the wind power plant is started from far to near and from near to far according to the electrical distance, respectively, in the embodiment of the present invention;
fig. 9, fig. 10 and fig. 11 are simulation diagrams of the total power of each wind farm matching the corresponding load, the output power of each energy storage power station and the bus voltage when the wind farm is started according to the optimal scheme of the electrical distance from near to far and combined with droop control, respectively.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The embodiment of the invention provides a control and optimization method for black start of a wind storage system, which comprises the following steps:
(1) the distributed wind storage system bottom control comprises the following steps: double-fed asynchronous wind power generator (DFIG) directional vector control and Energy Storage System (ESS) voltage and current double closed-loop control; and in the starting stage of black start, the voltage instruction of the energy storage system is increased from zero to the rated voltage of the system so as to inhibit the excitation inrush current generated by the switch-on no-load transformer.
(2) DFIG stator voltage tracking control: the given rotor converter current command is: i all right angledr＝-Us/ω1Lm,idrAnd (0) controlling the stator no-load potential to track the voltage of the power grid.
(3) Droop control of the distributed energy storage system: and the energy storage power station outputs active power and reactive power according to the droop coefficient, so that the power is distributed in proportion.
(4) Optimizing the starting sequence of the wind power plant: and each wind power plant is sequentially started from near to far according to the electrical distance so as to reduce the impact of the wind power plants on the energy storage power station during the black start. After the starting sequence is determined, all the wind power plants can be started one by one, and the black starting process is completed.
As shown in fig. 1, it is a flow chart of the whole process of black start of the wind storage system determined by the present invention.
As shown in fig. 2, the topological structure of the distributed wind storage system provided by the present invention includes three subsections, namely, a double-fed asynchronous wind generator DFIG, an energy storage system ESS and a comprehensive load.
As shown in fig. 3, an equivalent circuit model of a wind storage network with 11 independent nodes determined by the present invention is used for measuring an electrical distance from a wind top layer to an energy storage power station, and includes: current source I for wind farmwParallel reactance XwTo be equivalent; voltage source E for energy storage power stationesSeries reactance XesTo be equivalent; reactance X for transformerT(ii) a Impedance Z for power transmission lineLTo indicate.
Equivalent circuit modelEstablishing a nodal impedance matrix ZnetAnd further calculating the transfer impedance from each wind power plant to the energy storage power station:
Figure BDA0003550571530000081
grid-connected node voltage:
Figure BDA0003550571530000082
and comparing the grid-connected node voltage of each wind power plant to determine the black start sequence of each wind power plant.
As shown in fig. 4, the DFIG directional vector control includes:
(1.1) the stator side converter controls the stator to output active power and reactive power, the reference rotor dq axis voltage is obtained through a stator flux linkage directional vector control method, and then the active power P of the DFIG stator is achievedsAnd reactive power QsThe decoupling control of (1);
(1.2) the grid-side converter controls grid-connected active power and reactive power of a grid-side converter loop, the grid-side converter obtains dq axis reference voltage through grid voltage directional vector control, and then the DFIG grid-side output active power P is achievednetReactive power Q of sum network side converter loopsrThe decoupling control of (2).
Energy storage system topology as shown in fig. 5, the underlying ESS control method includes: the energy storage system is controlled through double closed-loop control, and then the voltage V on the direct current side of the fan is stabilizeddcThe inverter can conveniently realize the bidirectional exchange of power.
As shown in fig. 6, the energy storage droop control strategy includes a phase-locked loop module, active droop control, and reactive droop control. After coordinate transformation, active frequency droop control is added in d-axis control, and reactive voltage droop control is added in q-axis control. Establishing a primary voltage regulation process in an analogy power grid primary frequency regulation process to obtain active and reactive reference values, and obtaining dq decoupled internal potential reference value e through a power and current regulatord，eqThen is further prepared byAnd dq inverse transformation and SVPWM are used for controlling the switching tube.
Example (b):
the values of the various parameters of the system are shown in table 1:
TABLE 1
Figure BDA0003550571530000083
Figure BDA0003550571530000091
The sag factor of the energy storage plant is shown in table 2:
TABLE 2
Energy storage power station Bus where Reactive sag factor Active droop coefficient
Energy storage power station 1 5 8 4
Energy storage power station 2 10 12 6
Energy storage power station 3 11 5 2.5
Energy storage power station 4 1 1 0.5
Through modeling and calculation in the process, the grid-connected node voltage U of 4 wind power plants is finally obtainedw2、Uw3、Uw6、Uw7The voltage amplitudes are sorted according to the magnitude, and the magnitude relation is as follows:
Uw6＞Uw7＞Uw3＞Uw2
therefore, the black start sequence determined in the above way is 6-7-3-2, namely the lotus village-Niugishan-Yingzi Sai-Baolin Lifeng. The electric distance quantification performed by the method fully considers the influence of the self capacities of the lines, the transformers, the wind power plant and the energy storage power station in the system on the starting difficulty. As shown in fig. 7, each wind farm completes the grid connection at the time t is 2s, 4s, 6s, and 8s in sequence. Compared with fig. 7, in the simulation result corresponding to the starting mode shown in fig. 8, the waveforms of the active power and the reactive power obviously have smaller overshoot, which indicates that the impact brought to the power grid is minimum when the wind turbine is connected to the power grid. Starting from near to far according to the electrical distance can make the system have better transient process.
As shown in fig. 9, the total power of each wind farm and load responds according to the starting sequence, the shock generated in the starting process does not cause the collapse of the active and reactive levels of the system, and the used control strategy is effective. As shown in fig. 10, after droop control is added according to the coefficients in table 2, the energy storage power station outputs active power and reactive power according to the droop coefficients, so that proportional power distribution is realized. Fig. 11 shows waveforms of bus voltage and frequency during black start. According to the national standards of the people's republic of China: the variation of the grid voltage frequency is not more than 1% and the variation of the amplitude is not more than 5% in the deviation of the power quality-the frequency amplitude of the power system. Therefore, the starting mode meets the fluctuation limit of the voltage and the amplitude in the dynamic process, and ensures the electric energy quality in the starting process.
In general terms:
(1) the invention provides a method for determining the grid-connected sequence of each wind power plant in spatial distribution in the black start process based on a circuit equivalent model of a wind storage network, so as to ensure the minimum impact on an energy storage power station in the black start process; meanwhile, the stability of the wind storage system in the black starting process is improved by using the zero boost starting and DFIG smooth grid-connected technology of the energy storage power station. Therefore, the wind power station system can smoothly start each wind power station to form a stable wind power storage isolated network system by using the optimal starting sequence when the wind speed is appropriate
(2) The invention takes the difference of the capacities of the energy storage power stations into consideration, and utilizes the droop control strategy to enable each energy storage power station to distribute power in equal proportion according to the capacity of the energy storage power station, so that the capacity of the energy storage unit can be fully utilized. Meanwhile, droop control simulates the primary frequency modulation and voltage regulation process of a power grid, and reactive power and active power output by the inverter are adjusted according to system voltage and frequency variation. The stability of the system is enhanced.
Furthermore, those skilled in the art will appreciate that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks.
The embodiment of the invention also provides a control and optimization system for the black start of the wind storage system, which comprises the following components: a computer-readable storage medium and a processor;
the computer-readable storage medium is used for storing executable instructions;
the processor is used for reading executable instructions stored in the computer-readable storage medium and executing the control and optimization method for the black start of the wind storage system.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (8)

1. A control and optimization method for black start of a wind storage system is characterized by comprising the following steps:
(1) each energy storage power station adopts a droop control strategy and is started to rated voltage U in a zero boost modenEstablishing stable frequency and voltage for the system, and simultaneously charging a no-load line and a transformer in the system;
(2) putting auxiliary equipment of the wind power plant into use, and enabling the double-fed asynchronous wind driven generator to have an external voltage U in the step (1)nCarries out rotor grid connection under the support of the double-fed asynchronous wind driven generator and carries out rotor current i on the double-fed asynchronous wind driven generatorrd、irqControl is performed so that no-load electromotive force E of the stator winding0And bus voltage UnThe voltage tracking is carried out to realize the smooth grid connection of the subsequent fan;
(3) the stator of the doubly-fed asynchronous wind generator is connected to the power grid, the rotor-side converter is switched from the hollow load grid-connected mode to the MPPT control mode in the step (2) to capture maximum wind energy, and the stator-side converter stabilizes the direct-current side capacitor voltage UCAnd reactive power Q of grid connectionwindEnabling the wind power plant to finish self-starting and output with constant power;
(4) after the wind power plant finishes self-starting, putting corresponding loads into the wind power plant to form a stable wind storage island system for supplying power to local loads;
(5) establishing a mathematical model of a power supply network to be researched, and calculating the equivalent electrical distance from each wind power plant to an energy storage power station for optimizing the black start sequence of each wind power plant;
(6) and (5) sequentially executing the steps (2) - (4) to each wind power plant according to the black start sequence determined in the step (5) to finish the black start process.
2. The method according to claim 1, wherein the droop control in step (1) is used for simulating the primary frequency modulation process of a conventional synchronous generator, and the reactive power and the active power output by the inverter are adjusted according to the system voltage and frequency variation, and the voltage and frequency adjustment process is realized by the following objective equations:
Pref＝Pe-Dp(ωn-ω)
Qref＝Qe-Dq(Un-U)
obtaining a power instruction through the error of voltage and frequency, and obtaining an internal potential reference value of the energy storage system through a voltage-current double closed loop, wherein Pref、QrefFor a set active and reactive reference value, Pe、QeIs the actual output power of the inverter; omeganOmega is the rated frequency and the actual frequency of the system, UnU is the rated output voltage and the actual output voltage, Dp、DqP-omega and Q-V droop coefficients;
linearly increasing the output voltage command of the inverter from 0 to the rated system voltage UnAnd excitation inrush current generated when the no-load transformer is switched on is restrained, and the follow-up self-starting failure of the wind power plant caused by the excitation inrush current is prevented.
3. The method of claim 1, wherein in step (2), the no-load electromotive force of the stator winding is expressed by a rotor current as:
Figure FDA0003550571520000021
wherein L ismIs equivalent mutual inductance of stator and rotor windings, uds、uqsDq components of the stator winding voltage, respectively, if oriented in the stator voltage vector, should have uds＝Us，uqs＝0；iqr、idrIs a rotor current dq component, omega in the same coordinate system1For the synchronous rotating speed of the motor, a derivative term in the following steady state formula is 0, and a current instruction of a rotor winding obtained by combining the grid-connected requirement on the stator potential is as follows:
Figure FDA0003550571520000022
in the formula of UsAnd obtaining a voltage instruction of the rotor side converter for the rated voltage of the power grid through the voltage ring PI regulator so as to execute the no-load starting of the doubly-fed asynchronous wind driven generator.
4. The method according to claim 1, wherein the MPPT control mode in step (3) is specifically:
method for controlling mechanical power P of fan by adopting power feedback methodmechOptimum power-speed curve P for running in fanoptOn (omega), the control object is the stator output active power P1；
The transmission mechanism is approximately regarded as a rigid body, and the power of the system is balanced in a steady state:
Pmech-ωTf＝P1+PCu+PFe
in the formula: p1Outputting active power for the DFIG stator; j and TfRespectively an inertia time constant and a friction torque of the transmission mechanism; pFeAnd PCuThe iron loss and the stator and rotor copper loss of the doubly-fed asynchronous wind driven generator are respectively; continuously changing fan stator power instruction P in a certain wind speed range* 1(ω) to PmechAccording to PoptAnd (omega) is regularly changed, and maximum power tracking is realized.
5. Method according to claim 1, characterized in that in step (5) a mathematical model of the power supply network to be studied is established, the electrical distances being used to optimize the starting sequence of the wind farm, in particular comprising:
transforming an impedance network in the system into a network with only direct impedance between the wind power plant and the energy storage power station, and determining an n-order node impedance matrix Z of the systemnetI.e. the nodal admittance matrix YnetWherein n is the number of nodes of the network; each electrical element in the network is equivalent with the following model:
reactance X for transformerTEquivalently, neglecting its excitation branch Rm+jXmAnd a windingA resistance R;
impedance Z for power transmission lineLEquivalently, neglecting the capacitance to ground;
the energy storage power station adopts a v-f control strategy, an infinite voltage source is used for connecting an equivalent reactance model in series for equivalence, and in a per unit value system, the potential E of the equivalent voltage source is equivalent to the potential EesiAnd impedance xesiRespectively expressed as:
Eesi＝1
Figure FDA0003550571520000031
wherein SBIs the capacity base value of the system, SesiThe capacity of the energy storage power station connected to the node i;
a P-Q control strategy is adopted in the wind power plant, when the voltage of a power grid is assumed to be constant, an infinite current source is used for connecting an equivalent reactance model in parallel for equivalence, and the equivalent impedance is expressed as follows:
Figure FDA0003550571520000032
wherein SwiIs the wind farm capacity connected to node i.
6. The method according to claim 5, wherein the step (5) of calculating the equivalent electrical distance from each wind farm to the energy storage power station comprises:
calculating the transfer impedance between the wind power station at the node i and the energy storage power station, wherein the specific calculation formula is as follows:
Figure FDA0003550571520000041
wherein A is a set of node numbers connected with the energy storage, and Zi,jNode impedance matrix Z representing the entire networknetElement of the ith row and jth column, xesjRepresenting the equivalent impedance of the jth energy storage power station;
calculating the voltage of the wind power plant grid-connected node at the node i according to the transfer impedance, namely the equivalent electrical distance, wherein the specific calculation formula is as follows:
Figure FDA0003550571520000042
wherein EesiFor equivalent potential, x, of the ith energy-storage stationwiIs the equivalent impedance of the ith wind farm, ZwiTransfer impedance calculated for the above formula, grid-connected node voltage U of wind farmwiThe larger the power supply is, the stronger the reactive power supply capacity of the energy storage power station to the wind turbine is, the closer the reactive power electrical distance from the energy storage power station to the wind power plant is, and the earlier the wind power plant is started in the black start process, so that the start sequence of each wind power plant is determined.
7. The method according to any of claims 1 to 6, wherein the wind storage system comprises a rotor-side converter and a grid-side converter, wherein,
the rotor-side converter realizes decoupling control of active power and reactive power of a stator of the double-fed asynchronous wind driven generator through stator flux linkage directional vector control;
the grid-side converter realizes decoupling control of the active power output by the grid side of the double-fed asynchronous wind driven generator and the reactive power of a grid-side converter loop through grid voltage directional vector control.
8. A control and optimization system for black start of a wind storage system, comprising: a computer-readable storage medium and a processor;
the computer readable storage medium is used for storing executable instructions;
the processor is used for reading executable instructions stored in the computer-readable storage medium and executing the control and optimization method for the black start of the wind storage system according to any one of claims 1 to 6.
CN202210262419.9A 2022-03-16 2022-03-16 Control and optimization method and system for black start of wind storage system Pending CN114744747A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116154845A (en) * 2022-12-08 2023-05-23 中国石油大学(华东) Control method of H-bridge serial-parallel switching type forced excitation converter based on DAB

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116154845A (en) * 2022-12-08 2023-05-23 中国石油大学(华东) Control method of H-bridge serial-parallel switching type forced excitation converter based on DAB
CN116154845B (en) * 2022-12-08 2023-11-21 中国石油大学(华东) Control method of H-bridge serial-parallel switching type forced excitation converter based on DAB

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