CN116545039A - Method and system for determining equivalent comprehensive inertia of direct-drive fan and electronic equipment - Google Patents

Method and system for determining equivalent comprehensive inertia of direct-drive fan and electronic equipment Download PDF

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CN116545039A
CN116545039A CN202310796729.3A CN202310796729A CN116545039A CN 116545039 A CN116545039 A CN 116545039A CN 202310796729 A CN202310796729 A CN 202310796729A CN 116545039 A CN116545039 A CN 116545039A
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direct
inertia
fault
time
drive fan
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CN116545039B (en
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王彤
李鸿恩
孙振宇
王增平
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North China Electric Power University
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North China Electric Power University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • 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
    • H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • H02P9/10—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
    • H02P9/102—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load for limiting effects of transients
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
    • H02P9/10—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
    • H02P9/105—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load for increasing the stability
    • 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P2101/00—Special adaptation of control arrangements for generators
    • H02P2101/15—Special adaptation of control arrangements for generators for wind-driven turbines
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electric Motors In General (AREA)

Abstract

The invention provides a method, a system and electronic equipment for determining equivalent comprehensive inertia of a direct-drive fan, belonging to the field of power systems, wherein the method comprises the following steps: acquiring the fault occurrence time of a power grid, the real-time frequency of the power grid, the initial value of d-axis component of the current at the network side on a phase-locked loop coordinate system and the control parameters of a direct-driven fan at the fault recovery stage (the proportional gain of a phase-locked loop PI control link, the proportional gain of q-axis current at a machine side PI control link, the proportional gain of q-axis current at the network side PI control link, the differential gain of a virtual inertia control link and the direct-current side capacitance); determining total fault crossing time and total fault recovery time according to fault occurrence time and real-time frequency of a power grid; and determining the equivalent comprehensive inertia of the direct-drive fan according to the initial value of the d-axis component of the network side current on the phase-locked loop coordinate system, the control parameter, the total transient process duration, the total fault ride-through duration and the total fault recovery duration. The inertia estimation method and the inertia estimation device improve the accuracy of the inertia estimation of the direct-drive fan.

Description

Method and system for determining equivalent comprehensive inertia of direct-drive fan and electronic equipment
Technical Field
The invention relates to the field of power systems, in particular to a method, a system and electronic equipment for determining equivalent comprehensive inertia of a direct-drive fan in the whole process of power grid faults.
Background
The traditional power generation modes such as thermal power generation and the like are gradually replaced by new energy power generation. With the gradual increase of the new energy power generation ratio in the power system, the carbon emission is improved, the sustainable development is promoted, and meanwhile, the stable operation of the power system is also challenged. The new energy power generation device is connected with the power electronic equipment through the power electronic equipment, and the special physical structure of the power electronic equipment replaces the traditional synchronous machine and simultaneously changes the response characteristic of the power system. The new energy power generation device which is connected with the power electronic equipment is decoupled from the frequency of the power system, and inertia support cannot be actively provided for the power grid when the power electronic equipment is subjected to frequency disturbance, so that the total inertia of the power system in a double-high mode is greatly reduced. There is a need for new power systems that improve the effective inertia and improve the anti-interference capabilities of the power grid.
By adding virtual inertia control to the direct-drive fan, the direct-drive fan can have equivalent inertia. The virtual inertia control utilizes the frequency offset and the frequency change rate to control the fan to change the output of active power, and provides inertia support for the power system. In order to timely sense inertia change, the standby capacity of the system, energy storage equipment and a virtual inertia control mode are scientifically configured in power grid planning, and the equivalent inertia of the direct-drive fan needs to be evaluated. At present, in the method level, there are mainly inertia evaluation methods based on measurement data processing, electromechanical disturbance propagation, system identification and the like, and the inertia evaluation is performed by utilizing dynamic changes under small interference, and the change condition of inertia support in the fault process is not considered, so that when a fan is switched to fault crossing control, an additional frequency control strategy cannot respond to the change of system frequency. The fans cannot provide functions of additional active control such as inertia, primary frequency modulation and the like in the fault ride-through process, and the larger the range of the fans affected by faults is, the smaller the number of fans capable of providing inertia support is. And in the short circuit fault, the power grid voltage drops, and the normal control state is switched into the fault ride through control state, during which the additional virtual inertia controller cannot play a role in inhibiting frequency change, and the control system can play a role only when the control system is switched into the normal control again.
Therefore, unlike the inertia response process of the synchronous generator, the influence of the equivalent inertia control link of the direct-drive fan presents a time-varying characteristic. In the fault process, a fault crossing circuit is put into, the direct-current side capacitor voltage is controlled to be unchanged, the output variable of the machine side converter control system cannot be effectively transmitted, and the inertia support is severely restricted.
Disclosure of Invention
The invention aims to provide a method, a system and electronic equipment for determining equivalent comprehensive inertia of a direct-drive fan, which can improve the accuracy of inertia estimation of the direct-drive fan.
In order to achieve the above object, the present invention provides the following solutions:
the method for determining the equivalent comprehensive inertia of the direct-driven fan comprises the steps of:
acquiring the fault occurrence time of a power grid, the real-time frequency of the power grid, the initial value of the d-axis component of the current at the grid side on a phase-locked loop coordinate system and the control parameters of a direct-drive fan at the fault recovery stage; the control of the direct-driven fan when the power grid fails comprises a virtual inertia control link, a fault ride-through control link, a machine side PI control link, a phase-locked loop PI control link and a network side PI control link; the control parameters include: proportional gain of the phase-locked loop PI control link, proportional gain of q-axis current of the machine side PI control link, proportional gain of q-axis current of the network side PI control link, differential gain of the virtual inertia control link and direct current side capacitance;
Determining the transient process end time of the power grid according to the real-time frequency of the power grid;
determining the total duration of the transient process according to the fault occurrence time and the transient process ending time; the transient process of the power grid comprises a fault ride-through stage and a fault recovery stage;
acquiring the time for maintaining the upper limit value of the capacitor voltage at the direct current side in the transient process;
calculating the total fault ride-through time according to the time for maintaining the upper limit value of the direct-current side capacitor voltage in the transient process;
calculating the total fault recovery time according to the total transient process time and the total fault crossing time;
and determining the equivalent comprehensive inertia of the direct-drive fan according to the initial value of the d-axis component of the network side current on the phase-locked loop coordinate system, the control parameter, the total transient process duration, the total fault traversing duration and the total fault recovery duration.
In order to achieve the above purpose, the present invention also provides the following solutions:
a direct-drive fan equivalent comprehensive inertia determining system comprises:
the data acquisition unit is used for acquiring the fault occurrence time of the power grid, the real-time frequency of the power grid, the initial value of the d-axis component of the current at the grid side on the phase-locked loop coordinate system and the control parameter of the direct-driven fan at the fault recovery stage; the control of the direct-driven fan when the power grid fails comprises a virtual inertia control link, a fault ride-through control link, a machine side PI control link, a phase-locked loop PI control link and a network side PI control link; the control parameters include: proportional gain of the phase-locked loop PI control link, proportional gain of q-axis current of the machine side PI control link, proportional gain of q-axis current of the network side PI control link, differential gain of the virtual inertia control link and direct current side capacitance;
The end time determining unit is connected with the data acquisition unit and is used for determining the transient process end time of the power grid according to the real-time frequency of the power grid;
the transient total duration determining unit is respectively connected with the data acquisition unit and the ending time determining unit and is used for determining the total duration of the transient process according to the fault occurrence time and the transient process ending time; the transient process of the power grid comprises a fault ride-through stage and a fault recovery stage;
the time length determining unit is used for obtaining the time for maintaining the upper limit value of the direct-current side capacitor voltage in the transient process and calculating the total fault crossing time length according to the time for maintaining the upper limit value of the direct-current side capacitor voltage in the transient process;
the recovery time length determining unit is respectively connected with the transient total time length determining unit and the traversing time length determining unit and is used for calculating the total fault recovery time length according to the transient process total time length and the fault traversing total time length;
the comprehensive inertia determining unit is respectively connected with the data obtaining unit, the transient total duration determining unit, the traversing duration determining unit and the recovery duration determining unit and is used for determining the equivalent comprehensive inertia of the direct-drive fan according to the initial value of the d-axis component of the network side current on the phase-locked loop coordinate system, the control parameter, the transient total duration, the fault traversing total duration and the fault recovery total duration.
In order to achieve the above purpose, the present invention also provides the following solutions:
an electronic device comprises a memory and a processor, wherein the memory is used for storing a computer program, and the processor runs the computer program to enable the electronic device to execute the method for determining the equivalent comprehensive inertia of the direct-drive fan.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the method comprises the steps of firstly determining total fault ride-through time and total fault recovery time, and then determining equivalent comprehensive inertia of a direct-drive fan according to an initial value of d-axis component of network-side current on a phase-locked loop coordinate system, control parameters of the direct-drive motor (proportional gain of a phase-locked loop PI control link, proportional gain of q-axis current of a machine-side PI control link, proportional gain of q-axis current of a network-side PI control link, differential gain of a virtual inertia control link and direct-current side capacitance), total transient process time, total fault ride-through time and total fault recovery time. By taking the fault information into account in the inertia evaluation process, the accuracy of the evaluation is improved. And calculating equivalent comprehensive inertia through control parameters, steady-state working conditions and sectional time, wherein when harmonic waves and noise appear in measured data after disturbance occurs, a calculation result is not affected, and further, the robustness of direct-drive fan inertia evaluation is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments will be briefly described below.
Fig. 1 is a control schematic diagram of a direct drive fan.
Fig. 2 is a schematic diagram of transient process phase division.
Fig. 3 is a flowchart of the method for determining equivalent comprehensive inertia of the direct-drive fan.
FIG. 4 is a graph of the relationship among inertia, inertia combination, and integrated inertia.
Fig. 5 is a logic schematic diagram of the equivalent integrated inertia estimation process of the direct drive fan.
Fig. 6 is a block diagram of an improved four-machine two-zone system.
Fig. 7 is a schematic diagram of system frequency variation during a scene 1 simulation.
Fig. 8 is a schematic diagram of a dc side capacitor voltage change during a scenario 1 simulation.
Fig. 9 is a graph comparing the estimated value and the calculated value of the equivalent inertia in the fault recovery stage of scenario 1.
Fig. 10 is a graph comparing estimated values and calculated values of equivalent comprehensive inertia in the whole transient process of the scene 1.
Fig. 11 is a comparison diagram of frequency changes of the direct-drive fan and the equivalent synchronous machine set after the scene 1 fails.
Fig. 12 is a graph comparing the estimated value and the calculated value of the equivalent inertia in the scene 2 fault recovery stage.
Fig. 13 is a graph comparing estimated and calculated values of equivalent integrated inertia in the entire transient process of scene 2.
Fig. 14 is a block diagram of a modified IEEE39 node system.
FIG. 15 is a schematic diagram of system frequency variation during a simulation of a modified IEEE39 node system.
FIG. 16 is a schematic diagram of DC side capacitor voltage variation during simulation of a modified IEEE39 node system.
FIG. 17 is a graph of estimated and calculated equivalent inertia for a failure recovery phase of a modified IEEE39 node system.
FIG. 18 is a graph comparing estimated and simulated values of equivalent integrated inertia throughout transient of a modified IEEE39 node system.
Fig. 19 is a schematic diagram of an equivalent comprehensive inertia determining system of a direct-drive fan.
Symbol description:
G1-G10-generators, PMSG-direct-drive wind turbines, L1-L2-loads and 1-39-nodes.
201, data acquisition unit, 202, end time determining unit, 203, transient total duration determining unit, 204, traversing duration determining unit, 205, recovery duration determining unit, 206, comprehensive inertia determining unit.
Detailed Description
The invention aims to provide a method, a system and electronic equipment for determining equivalent comprehensive inertia of a direct-drive fan, which can more accurately quantify the equivalent inertia supporting effect of the direct-drive fan by examining the control links and dynamic changes in the fault process.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
The direct-drive fan is connected with the grid through the back-to-back double PWM converters, so that energy is utilized to the greatest extent, safe operation of an electric power system is promoted, and the converters and the direct-current side capacitor adopt a plurality of complicated control links. These control links are constrained by each other, and when the power system is operating in different states, the primary control links will switch. The control principle of the direct-drive fan is shown in fig. 1, and when the power system fails, the inertia response characteristic of the direct-drive fan is affected by the switching variation of the virtual inertia control and the fault ride-through control.
When the DC side capacitor voltage V dc Exceeding a set maximum voltage V dcmax When the fault ride-through strategy is automatically put into operation, virtual inertia control continues to act at the moment, but the control effect is shielded; when the direct-current side capacitor voltage is recovered to be lower than or equal to the maximum voltage, the fault ride-through strategy is automatically thrown out, and the action effect of virtual inertia control is recovered. Wherein the fault isThe ride-through control includes the consumption of active power by the chopper current input and the unloading resistor.
The switching process and the action principle of the direct-driven fan control system after the power grid faults and the inertia response change process are specifically analyzed:
After the fault occurs, the frequency of the power system is suddenly changed, the virtual inertia controls the input frequency deviation amount and the frequency change rate, the active power change amount is output, and the direct-drive fan provides equivalent inertia for the power system. Meanwhile, after the fault occurs, the voltage of the fan end is suddenly changed, and the output power of the grid-side converter is severely limited. However, the machine side converter output power is unchanged and a large active power difference accumulates on the direct current side capacitor, resulting in a rapid rise in its voltage to the upper limit of the standard range. At this time, the low voltage ride through circuit is put into operation, and the direct current side capacitor voltage is considered to be stable at the upper voltage limit in the electromechanical time scale until the direct current side capacitor voltage is restored to be within the standard range. At this stage, the virtual inertia control still outputs an active power variation according to the frequency information, and the variation controls the q-axis current, thereby controlling the q-axis voltage and the machine side converter to output active power, and finally controls the direct-current side capacitor voltage to transmit to the network side.
From the above analysis, it is known that the capacitor voltage at the dc side is kept unchanged during the low voltage ride through by the low voltage ride through strategy, so that the amount of change in the virtual inertia control output cannot be transferred to the grid side, and the equivalent inertia of the direct drive fan is zero at this stage for the grid.
When the voltage of the direct-current side capacitor is recovered, the low-voltage ride-through circuit is thrown out, and the excessive capacitive current can cause the voltage of the machine end to continuously rise beyond the standard range due to the delay throwing out of the reactive compensation device, the power grid reversely injects energy into the grid-side converter, the output active power of the machine-side converter is still unchanged, and a large amount of active power difference is accumulated on the direct-current side capacitor, so that the voltage of the machine-side converter reaches the upper limit again. At this time, the high voltage ride through circuit is put into operation, and the direct current side capacitor voltage is considered to be stable at the upper voltage limit in the electromechanical time scale until the direct current side capacitor voltage is restored to be within the standard range. In this stage, the virtual inertia control effect cannot be transmitted to the net side, and the equivalent inertia of the direct-drive fan is zero.
When the direct-current side capacitor voltage is recovered, the high-voltage ride-through circuit is thrown out, the virtual inertia control transmits the output variable quantity to the net side again through the direct-current side capacitor voltage, and the direct-drive fan continues to provide equivalent inertia for the system until the system frequency is recovered to the rated value. At this time, virtual inertia is controlled to be thrown out, and the direct-driven fan control system restores the structure in a steady state.
According to the analysis, the transient process after the fault is generated can be divided into four phases, namely a fault initial phase, a low voltage ride-through phase, a high voltage ride-through phase and a fault recovery phase. Transient phase division is shown in fig. 2.
The initial fault phase is a time period from the occurrence of a fault to the input of the low voltage ride through circuit. In this stage, virtual inertia control plays a dominant role, and the direct-drive fan provides equivalent inertia to the system according to frequency variation.
The low voltage ride through phase and the high voltage ride through phase may be combined into a fault ride through phase. The fault ride-through phase is a time phase of thoroughly throwing from the fault ride-through circuit to the fault ride-through circuit. In this stage, the fault ride-through strategy dominates, and the equivalent inertia that the direct drive fan provides to the system is zero.
The fault recovery phase is a time phase in which the frequency thoroughly thrown from the fault ride through circuit to the power system is recovered to a rated value. In this stage, virtual inertia control resumes the dominant role, and the direct drive fan continues to provide equivalent inertia to the power system according to frequency variation.
According to the analysis, the equivalent inertia response characteristics of the direct-drive fan in the initial fault stage and the recovery fault stage are the same, so that the initial fault stage can be considered together in the category of the recovery fault stage in the subsequent inertia estimation.
Therefore, in the transient process after the fault occurs, the equivalent inertia of the direct-drive fan has two different response characteristics, namely an inertia response characteristic in a fault crossing stage and a fault recovery stage. In the fault ride-through stage, the equivalent inertia of the direct drive fan is zero. In the fault recovery stage, virtual inertia control responds to the frequency change of the power system, and is transmitted to a grid-connected point through control links such as a machine side converter, a direct-current capacitor, a grid side converter, a phase-locked loop and the like, so that the active power output by a direct-drive fan is changed, and equivalent inertia is provided for the system.
In fig. 1, V in the control of the grid-side converter dcref I is the reference value of the capacitor voltage at the direct current side wqref For q-axis component reference value, i of net side current in phase-locked loop coordinate system wdref For d-axis component reference value, i of network side current in phase-locked loop coordinate system wd For d-axis component, i of net side current in phase-locked loop coordinate system wq For d-axis component of net side current in phase-locked loop coordinate system, Q weref For inductive reactive power reference, Q we For inductive reactive power, K p_Qw For the proportional gain of inductive reactive power in the network-side PI control link, K i_Qw For integrating gain of inductive reactive power in network-side PI control link, K p_twd The proportional gain of d-axis voltage of the network-side PI control link is K i_twd The integral gain of d-axis voltage of the network-side PI control link is K p_twq For the proportional gain of q-axis voltage of the network-side PI control link, K i_twq The integral gain of the q-axis voltage of the network-side PI control link is obtained.
Example 1
As shown in fig. 3, this embodiment provides a method for determining equivalent comprehensive inertia of a direct-drive fan, including:
s1: and acquiring the fault occurrence time of the power grid, the real-time frequency of the power grid, the initial value of the d-axis component of the current at the grid side on the phase-locked loop coordinate system and the control parameters of the direct-drive fan in the fault recovery stage. The control of the direct-driven fan when the power grid fails comprises a virtual inertia control link, a fault ride-through control link, a machine side PI control link, a phase-locked loop PI control link and a network side PI control link. The control parameters include: proportional gain of the phase-locked loop PI control link, proportional gain of q-axis current of the machine side PI control link, proportional gain of q-axis current of the network side PI control link, differential gain of the virtual inertia control link and direct current side capacitance.
S2: and determining the transient process ending time of the power grid according to the real-time frequency of the power grid.
Specifically, for any moment after the fault occurs, if the absolute value of the difference value between the frequency of the power grid and the reference frequency at the current moment is smaller than the frequency fluctuation threshold value, the current moment is the transient process ending moment. And the transient process ending time is the time when the power grid is recovered to be stable.
Since inertia is examined on the suppression effect on frequency disturbance, the magnitude of frequency fluctuation is used as a criterion for judging whether the power grid is stable or not, namelyWherein f is the frequency of the power grid, f ref For reference frequency->Is the frequency fluctuation threshold. Considering the uncontrollable switching of the third category of loads in the grid, in the present invention +.>Are all taken as 10 -3 。
S3: and determining the total duration of the transient process according to the fault occurrence time and the transient process ending time. The transient process of the power grid comprises a fault crossing stage and a fault recovery stage. Regarding the occurrence of faults to the system stability as the whole transient process, setting the total duration of the transient process as T, and then T=t 2 -t 1, wherein ,t1 For the moment of occurrence of failure, t 2 Is the transient process end time.
S4: and acquiring the time for maintaining the upper limit value of the capacitor voltage at the direct current side in the transient process.
S5: and calculating the total fault ride-through time according to the time for maintaining the upper limit value of the direct-current side capacitor voltage in the transient process.
S6: and calculating the total fault recovery time according to the total transient process time and the total fault crossing time. Specifically, as can be seen from the above analysis, on the electromechanical transient time scale, the dc side capacitor voltage is considered to stabilize at the upper voltage limit during the fault ride through. Therefore, the total fault ride-through time period can be calculated by calculating the time when the DC side capacitor voltage maintains the upper limit valueAnd (5) determining. The total time of fault recovery can be determined by the total time of transient process and the total time of fault crossing, namely T 1 =T-T 2. wherein ,T1 For the total time length of fault recovery, T 2 Is the total duration of fault ride-through.
S7: and determining the equivalent comprehensive inertia of the direct-drive fan according to the initial value of the d-axis component of the network side current on the phase-locked loop coordinate system, the control parameter, the total transient process duration, the total fault traversing duration and the total fault recovery duration.
Further, in order to embody the continuous action effect of inertia over a certain time, the inertia combination concept is introduced. Inertia is the continuous effect of the generator rotor kinetic energy over a period of time for varying the active power output. Mathematically, the time accumulation effect can be effectively represented by a fixed integral. S7 specifically comprises the following steps:
S71: and calculating the equivalent inertia sum of the direct-drive fan in the fault ride-through stage according to the total fault ride-through time. According to the analysis, the equivalent inertia of the direct-drive fan in the fault-ride-through stage is always 0, so that the equivalent inertia of the direct-drive fan in the fault-ride-through stage is combined into:； wherein ,/>For equivalent inertia combination of direct-drive fans in fault ride-through stage, H 2 And (t) is an expression of equivalent inertia in the fault ride-through stage.
S72: and calculating the equivalent inertia combination of the direct-drive fan in the fault recovery stage according to the initial value of the d-axis component of the network side current on the phase-locked loop coordinate system, the control parameter and the total fault recovery time.
Further, in S72, the equivalent inertia of the direct-drive fan in the fault recovery stage is calculated first, and then the equivalent inertia combination is calculated. The direct-drive fan realizes stator voltage directional control by means of a phase-locked loop (PLL) so that the q-axis of the rotating coordinate system coincides with the stator voltage vector. The phase-locked loop can rapidly and accurately track the phase of the voltage of the grid-connected point of the fanFrequency information. Let it be assumed that the net side voltageReference angular velocity->According to the closed-loop control process of the phase-locked loop, the transfer function under the frequency domain is obtained as follows: />； wherein ,/>For the q-axis phase angle in the phase-locked loop coordinate system, < > >For the net side voltage phase angle, K p_pll Is the proportional gain, K of the phase-locked loop PI control link i_pll The integral gain of the phase-locked loop PI control link is shown, and s is the Laplacian.
When the dynamic process of the phase-locked loop is considered, the reference coordinate system of the phase-locked loop is used for phase-locking angular velocityThe phase-locked loop cannot accurately track the network side voltage unlike the synchronous angular velocity, so that a phase difference is generated between the q-axis of the phase-locked loop coordinate system and the network side voltage. Accordingly, the d-axis component of the network side voltage on the phase-locked loop coordinate system and the q-axis component of the network side voltage on the phase-locked loop coordinate system can be obtained: />； wherein ,uwd U is the d-axis component of the network side voltage on the phase-locked loop coordinate system w For the network side voltage u wq Is the q-axis component of the net side voltage in the phase locked loop coordinate system. At steady state, the->。
Thus, the steady-state values of the net-side voltage d, q-axis components and the incremental expression at transient can be derived from the above equation:
；
wherein the subscript "0" represents an initial value, i.e., a steady state value, the symbol ""means increment, u wd0 For the initial value of d-axis component of network side voltage on phase-locked loop coordinate system, u wq0 For the initial value of the q-axis component of the network-side voltage in the phase-locked loop coordinate system,/for the network-side voltage>For the d-axis component increment of the network side voltage on the phase-locked loop coordinate system, +. >For the q-axis component increment of the network side voltage on the phase-locked loop coordinate system, +.>For the q-axis phase angle increment in the phase locked loop coordinate system, is->Is the net side voltage phase angle increment.
The electromagnetic power output by the direct-drive fan can be obtained by calculation through network side voltage and network side current, and the incremental expression of the electromagnetic power can be written according to the electromagnetic power:； wherein ,output electromagnetic power increment for network side, i wd0 For the initial value of d-axis component, i of network side current on phase-locked loop coordinate system wq0 For the initial value of the q-axis component of the network-side current in the phase-locked loop coordinate system,/for the network-side current>For d-axis component increment of network side current on phase-locked loop coordinate system, +.>For the q-axis component delta of the net side current on the phase locked loop coordinate system.
Substituting the steady state values of d and q axis components of the network side voltage and the increment expression in transient state into a calculation formula of the network side output electromagnetic power increment to obtain the following steps:。
because the current inner loop control changes rapidly, under the electromechanical transient time scale, the current i is considered to always follow the current given value i ref I.e. i=i ref ，，/>For current increment, +.>Is the increment of the current set value. Thus, according to the control link of the current of the q-axis of the grid side of the current transformer in fig. 1, it is possible to obtain:； wherein ,Kp_vdc For the proportional gain of q-axis current of the network-side PI control link, K i_vdc Integration gain of q-axis current for network-side PI control link,/, for>Is the capacitor voltage increment at the direct current side of the converter.
The DC side capacitor voltage can be calculated by differential equation, and the increment expression is written according to the differential equation:
； wherein ,/>The electromagnetic power increment is output for the machine side converter, C is direct current side electricitySize of the container.
According to the electromagnetic torque equation of the direct-drive fan, the side electromagnetic power P of the direct-drive fan can be obtained pme ：
； wherein ,/>For rotor speed, L d Is a direct axis reactance, L q For quadrature reactance, i pmd For the d-axis component, i, of the machine side current in the phase-locked loop coordinate system pmq For the q-axis component of the machine side current in the phase-locked loop coordinate system, +.>Is a constant flux linkage of the permanent magnet.
Since the machine side current transformer adopts the stator d-axis current zero control, the machine side d-axis current increment，/>The delta is given for the machine side d axis current. Thus, the incremental expression for machine side electromagnetic power can be obtained as: />； wherein ,/>For the initial value of the rotor speed, & lt & gt>Delta for the q-axis component of the machine side current on the phase locked loop coordinate system.
The set value of the machine side q-axis current of the direct-driven fan under virtual inertia control is determined by common control of three parts of power, and the set value is respectively: the virtual inertia control responds to the active power output by the frequency change, the active power sent by the maximum power tracking control and the electromagnetic power actually output by the machine side, and the following formula is adopted:
；
wherein ,ipmqref For the set value of the machine side q axis current, K p1 For proportional gain of q-axis current of machine side PI control link, P vic Active power, P, issued for virtual inertia control max The active power sent by the maximum power tracking control is a fixed value, K, under the electromechanical transient time scale i1 The integral gain of the q-axis current is controlled for the machine side PI.
Thus, the delta of machine side q-axis currentThe expression is:；/>active power delta issued for virtual inertia control.
And then obtain:。
the virtual inertia control measures the system frequency by estimating the rotation angular velocity of the dq coordinate system through the phase-locked loop, and changes the output of active power according to the frequency change rate and the frequency offset, and the increment expression is as follows:； wherein ,Kp_vic For proportional gain of virtual inertia control link, K d_vic Differential gain for virtual inertia control element, +.>Is the increment of the rotational angular velocity of the phase-locked loop.
Combining the formulas to obtain the increment relation between the electromagnetic power output by the direct-driven fan and the rotation angular speed of the phase-locked loop:； wherein ,，/>。
the rotational angular velocity of a phase-locked loop of the direct-drive fan and the output electromagnetic power of a network side are respectively analogized into the rotor angular velocity and the electromagnetic power of a synchronous generator, and according to the incremental expression of a rotor motion equation, the expression of the equivalent inertia of the direct-drive fan under the frequency domain can be obtained as follows:
；
H 1 The transfer function is a transfer function, which shows that the equivalent inertia of the direct-driven fan is influenced by the common effects of the operation condition, the rotation speed control, the direct-current capacitance, the virtual inertia control, the phase-locked loop parameter and the converter control, and has time-varying characteristics. The above equation can be simplified by using the initial theorem, and the initial value of the time domain function is obtained from the image function of the frequency domain. Since the model is built by local linearization of the nonlinear system at equilibrium, a simplified approach is reasonable. At this time, the equivalent inertia of the direct-drive fan under the per unit value is obtained as follows:
。
by adopting the method, the equivalent inertia of the direct-drive fan is related to the phase-locked loop parameters, and the equivalent inertia can be increased by reducing the phase-locked loop parameters. Due to the shielding effect of the direct-current side capacitor on the machine side device, the capacitor size and the equivalent inertia show a negative correlation. Increasing the virtual inertia control parameter can increase the equivalent inertia, and larger differential gain can make the virtual inertia control react more quickly to frequency changes. Changing the control and operation conditions of the converter can also affect the equivalent inertia of the direct-drive fan.
And then the equivalent inertia combination of the direct-drive fan in the fault recovery stage is calculated by adopting the following formula:
；
wherein ,For equivalent inertia combination of direct-drive fans in fault recovery stage, T 1 For the total time length of fault recovery, H 1 (t) is an expression of the equivalent inertia of the fault recovery stage, i wd0 For the initial value of d-axis component of network side current on phase-locked loop coordinate system, K p_pll Is the proportional gain, K of the phase-locked loop PI control link p1 For proportional gain of q-axis current of machine side PI control link, K p_vdc For the proportional gain of q-axis current of the network-side PI control link, K d_vic The differential gain of the virtual inertia control link is C is the direct-current side capacitance.
S73: and calculating the equivalent comprehensive inertia of the direct-drive fan according to the equivalent inertia combination of the direct-drive fan in the fault ride-through stage, the equivalent inertia combination of the direct-drive fan in the fault recovery stage and the total duration of the transient process.
The equivalent comprehensive inertia of the direct-drive fan is defined as the equal dividing effect of the equivalent inertia of the direct-drive fan in time in the whole transient process. The inertia supporting effect of the direct-driven fan on restraining the system frequency change in the whole transient process can be measured, and the inertia supporting effect is equivalent to that of synchronous generators with the same capacity and the same inertia in the same time. The relationship among inertia, inertia combination and integrated inertia is shown in fig. 4.
Specifically, the following formula is adopted to calculate the equivalent comprehensive inertia of the direct-drive fan:
；
wherein ,HT Is the equivalent comprehensive inertia of the direct-drive fan,equivalent inertia of direct-drive fan in fault recovery stageMeasuring and combining, treating the wind up>The equivalent inertia of the direct-drive fan in the fault ride-through stage is combined.
According to the calculation formula of the equivalent comprehensive inertia, the equivalent comprehensive inertia of the direct-drive fan in the whole transient process is influenced by fault information and fault crossing capacity. The fault information will affect the switching of the fault ride-through strategy and the duration of the transient. The stronger the fault ride-through capability is, the shorter the transient duration is, and the shorter the virtual inertia control is shielded, the equivalent comprehensive inertia of the direct-drive fan is affected.
In the calculation formula of the equivalent comprehensive inertia,and the part is determined by the operation working condition of the direct-drive fan and the phase-locked loop parameters, and under the same fault condition, if the phase-locked loop parameters of the direct-drive fan are unchanged, the normal steady-state operation is kept before the fault occurs, and the part inertia is unchanged. />And is determined by the structural parameters, control parameters and virtual inertia control of the converter. By changing the relevant control parameters, the inertia value of the part can be changed, and the equivalent comprehensive inertia of the direct-drive fan is further changed. Both parts of inertia are related to fault information, both of which change when the fault condition changes. The fault condition is changed, the total time of the transient process and the time of the fault crossing stage are changed, and the values of the total time and the time of the fault crossing stage are changed. Therefore, in the process of considering the fault information in the inertia evaluation, the accuracy of the equivalent comprehensive inertia evaluation can be further improved. The logic flow of the equivalent integrated inertia estimation of the direct drive fan is shown in fig. 5.
The simulation verification is carried out on the equivalent comprehensive inertia estimation method of the direct-drive fan by adopting a four-machine two-zone system. In the simulation process, the equivalent inertia of the fan in a period of time is calculated by using a mathematical integration method, so that the calculated value gradually approaches to the actual inertia value. And comparing the calculated value obtained by simulation with the estimated value obtained by adopting the estimation method of the invention for verification.
The test system adopts an improved four-machine two-area system, as shown in fig. 6, G1 to G4 are all generators, PMSG is a direct-drive wind turbine generator, 1 to 12 are all nodes, and L1 and L2 are all loads. During the simulation, the step size was set to 0.001 seconds.
Scene 1: at t=0.5 seconds the system fails, i.e. t 1 =0.5 seconds; the fault ends at t=0.53 seconds. The system frequency change and the direct-current side capacitance voltage change obtained through simulation are shown in fig. 7 and 8.
From the frequency simulation data, when t>At the time of 2.072 seconds, the time of day,at this point the system enters a new steady state, i.e. t 2 = 2.072 seconds. Thus, the transient total duration is t=t 2 -t 1 = 2.072-0.5= 1.572 seconds. From the DC capacitor voltage simulation data, when 1.06<t<1.579, the direct-driven fan is in a fault ride-through state, i.e. T 2 =1.579-1.06=0.519 seconds, therefore, T 1 = 1.572-0.519=1.053 seconds.
In the fault ride-through stage, the fan inertia is of a very small order of magnitude, subject to angular frequency harmonics and noise. If the harmonic wave and noise influence is ignored, the inertia of the fault crossing stage is 0, and the inertia accords with the estimated value of the stage. This indicates that the direct-drive fan cannot provide inertia support for the power grid at this stage, and the comprehensive inertia support capability of the fan is greatly weakened, so that the dynamic process at this stage needs to be considered when the inertia evaluation is performed on the fan. According to the control parameters of the direct-drive fan, the virtual inertia controls the differential gain K d_vic Proportional gain K of q-axis current of machine side PI control link= -4 p1 =0.1, proportional gain K of q-axis current of net-side PI control link p_vdc Proportional gain K of phase-locked loop PI control link=0.5 p_pll -0.1, the dc capacitance is 50pF. Obtaining the net side d-axis current i in steady state according to simulation wd0 = -0.1192. Substituting the values into an expression of equivalent inertia of the direct-drive fan in the fault recovery stage to obtain the faultAs shown in fig. 9, the calculated result of the inertia estimation value of the obstacle recovery stage is identical to the calculated equivalent inertia of the estimation method according to the present invention, that is, the expression of the present invention can better describe the equivalent inertia supporting effect of the fault recovery stage.
Therefore, the equivalent inertia response change process of the direct-drive fan after the fault occurs is consistent with the theoretical analysis. The equivalent inertia during fault ride-through is 0, which indicates that the fault ride-through strategy dominates the control of the dc side capacitor voltage at this stage, and the active change effect of the machine side is masked. As can be seen from fig. 9, the direct-driven fans in the initial fault stage and the recovery fault stage have the capability of providing equivalent inertia support to the system, and the inertia is the result of the combined actions of steady-state working conditions, phase-locked loop parameters, virtual inertia control, direct-current side capacitance and converter control parameters. This means that virtual inertia control dominates at this stage, active power variation is controlled according to phase-locked loop information, and transferred to the grid through capacitors and inverters. In summary, the analysis of the equivalent inertia response characteristic of the direct-drive fan accords with the actual simulation result.
Substituting the time parameter and the control parameter into a calculation formula of the equivalent comprehensive inertia of the direct-drive fan to obtain the equivalent comprehensive inertia of the direct-drive fan in the whole transient process, wherein the estimated result is H T = 0.8014. A comparison of this with the calculation results is shown in fig. 10. The direct-drive fan is replaced by the synchronous generator with the same capacity and the obtained inertia, the same fault of the power grid is set, and simulation pairs of system frequency change are shown in FIG. 11.
As can be seen from fig. 10, the calculated equivalent inertia of the direct-drive fan is. Compared with the estimation result obtained by the invention, the absolute error is 0.0705, and the relative error is 0.0808. As can be seen from fig. 11, the replaced frequency variation curve is very close to the frequency response curve of the simulated actual output, fitting on the dynamic course of the frequency disturbance and the frequency deviation towards steady stateThe degree is higher. Therefore, the estimation method has higher accuracy, can meet the requirement of inertia estimation, and accurately estimates the equivalent comprehensive inertia of the direct-drive fan from the occurrence of faults to the stability of the system on the whole time scale.
Scene 2: t is t 1 Still 0.5 seconds, the fault duration is prolonged, and the fault ends when t=0.65 seconds is set.
The control parameters of each control link are kept unchanged, and the frequency change and the direct-current side capacitance voltage change of the system are observed. From the frequency simulation data, when t>At the time of 2.169 of a second,at this point the system enters a new steady state, i.e. t 2 =2.169 seconds. Thus, the transient total duration is t=t 2 -t 1 =2.169-0.5=1.669 seconds. According to the DC capacitance voltage simulation data, when 0.551<t<0.651、0.826<t<1.166 and 1.747<t<1.994 the direct-drive fan is in a fault ride-through state, i.e., T 2 = (0.651-0.551) + (1.166-0.826) + (1.994-1.747) =0.687 seconds, thus, T 1 =1.669-0.687=0.982 seconds. Substituting the values into a calculation formula of the equivalent comprehensive inertia of the direct-drive fan to obtain the equivalent comprehensive inertia of the direct-drive fan in the whole transient process, wherein the estimated result is H T = 0.6980. The equivalent inertia calculation pair of the direct-driven fan in the fault recovery stage is shown in fig. 12, and the equivalent comprehensive inertia estimation value and calculation value pair of the direct-driven fan in the whole transient process is shown in fig. 13. And replacing the direct-drive fan with the synchronous generator with the same capacity and the obtained inertia, setting the same faults of the power grid, and comparing simulation results of the system frequency change.
The equivalent inertia of the direct-drive fan obtained through calculation is as follows. Compared with an estimated result obtained by an equivalent comprehensive inertia calculation formula of the direct-drive fan, the absolute error of the direct-drive fan is 0.0458, and the relative error of the direct-drive fan is 0.0656. The system frequency change after equivalent replacement has higher fitting degree of an actual system. Therefore, the result obtained by calculation by adopting the formula provided by the invention still has higher accuracy.
According to the results, the same control structure and control parameters and the same steady state operation state have different faults, and the equivalent comprehensive inertia of the direct-drive fan is different. The transient process time and the different stage time in the transient process under different faults are different, and the inertia response characteristics of the direct-drive fan at different time stages are different, so that the equivalent comprehensive inertia of the direct-drive fan in the whole transient process under the combined action of different stages is different. Therefore, by considering the inertia response characteristics in the fault process, the accuracy of the inertia estimation of the direct-drive fan can be improved.
The method for determining the equivalent comprehensive inertia of the direct-drive fan provided by the invention is verified by simulation by adopting an IEEE39 node system.
The test system employs a modified IEEE39 node system, as shown in fig. 14, 1 to 39 are nodes, G1 to G10 are generators, and PMSG is a direct drive fan group. During the simulation, the step size was set to 0.001 seconds.
When t=1 second, the system fails, and when t=1.1 seconds, the failure ends. The system frequency change and the direct-drive fan direct-current side capacitor voltage change obtained according to the simulation are shown in fig. 15 and 16. From the frequency simulation data, when t>At the time of 13.452 seconds, the time of day,at this point the system enters a new steady state, i.e. t 2 = 13.452 seconds. Thus, the transient total duration is t=t 2 -t 1 = 13.452-1= 12.452 seconds. From the DC capacitor voltage simulation data, it can be obtained when 1.02<t<1.102 and 1.933<t<2.096 the direct-drive fan is in a fault ride-through state, i.e., T 2 = (1.102-1.02) + (2.096-1.933) =0.245 seconds, therefore, T 1 = 12.542-0.245= 12.297 seconds. The values are substituted into a calculation formula of the equivalent comprehensive inertia of the direct-drive fan, so that the equivalent comprehensive inertia of the direct-drive fan in the whole transient process can be obtained, and the estimated result is H T = 1.2551. Therefore, it isThe simulation pair of equivalent inertia of the direct-drive fan in the obstacle recovery stage is shown in fig. 17, and the simulation pair of equivalent comprehensive inertia estimated value and simulation value of the direct-drive fan in the whole transient process is shown in fig. 18. And replacing the direct-drive fan with the synchronous generator with the same capacity and the obtained inertia, setting the same faults of the power grid, and comparing simulation results of the system frequency change.
The equivalent inertia of the direct-drive fan obtained through calculation is as follows. Compared with the estimated result obtained by the calculation formula provided by the invention, the absolute error is 0.0517, and the relative error is 0.0396. The system frequency change after equivalent replacement has higher fitting degree with the actual system. Therefore, in the IEEE39 node system, the result obtained by calculation of the invention still has higher accuracy.
According to the simulation result, the equivalent comprehensive inertia determination method has higher accuracy and universality for faults of different degrees. Compared with the traditional inertia estimation method, the method can obtain the equivalent inertia of the direct-drive fan more quickly and effectively, and greatly saves simulation time. Because the equivalent comprehensive inertia is obtained through calculation of control parameters, steady-state working conditions and sectional time, compared with the traditional inertia estimation method, when harmonic waves and noise appear in measured data after disturbance occurs, the estimation result is not affected. Therefore, the method has high robustness.
Example two
As shown in fig. 19, the equivalent comprehensive inertia determining system of the direct-drive fan provided in this embodiment includes: the system comprises a data acquisition unit 201, an end time determining unit 202, a transient total duration determining unit 203, a crossing duration determining unit 204, a recovery duration determining unit 205 and a comprehensive inertia determining unit 206.
The data obtaining unit 201 is configured to obtain a fault occurrence time of the power grid, a real-time frequency of the power grid, an initial value of a d-axis component of a current at a grid side on a phase-locked loop coordinate system, and a control parameter of the direct-driven fan at a fault recovery stage.
The control links of the direct-drive fan when the power grid fails comprise a virtual inertia control link, a fault ride-through control link, a machine side PI control link, a phase-locked loop PI control link and a network side PI control link.
The control parameters include: proportional gain of the phase-locked loop PI control link, proportional gain of q-axis current of the machine side PI control link, proportional gain of q-axis current of the network side PI control link, differential gain of the virtual inertia control link and direct current side capacitance.
The end time determining unit 202 is connected to the data obtaining unit 201, and the end time determining unit 202 is configured to determine an end time of a transient process of the power grid according to a real-time frequency of the power grid.
The transient total duration determining unit 203 is respectively connected to the data obtaining unit 201 and the end time determining unit 202, and the transient total duration determining unit 203 is configured to determine a transient total duration according to the fault occurrence time and the transient process end time. The transient process of the power grid comprises a fault crossing stage and a fault recovery stage.
The time duration determining unit 204 is configured to obtain a time for maintaining the upper limit value of the dc side capacitor voltage during the transient, and calculate the total time duration of fault ride-through according to the time for maintaining the upper limit value of the dc side capacitor voltage during the transient.
The recovery time length determining unit 205 is connected to the transient total time length determining unit 203 and the traversing time length determining unit 204, respectively, where the recovery time length determining unit 205 is configured to calculate a total fault recovery time length according to the transient total time length and the total fault traversing time length.
The comprehensive inertia determining unit 206 is respectively connected to the data obtaining unit 201, the transient total duration determining unit 203, the traversing duration determining unit 204, and the recovering duration determining unit 205, where the comprehensive inertia determining unit 206 is configured to determine an equivalent comprehensive inertia of the direct-driven fan according to an initial value of a d-axis component of the network side current on a phase-locked loop coordinate system, the control parameter, the transient total duration, the fault traversing total duration, and the fault recovering total duration.
Compared with the prior art, the equivalent comprehensive inertia determining system of the direct-drive fan provided by the embodiment has the same beneficial effects as the equivalent comprehensive inertia determining method of the direct-drive fan provided by the embodiment I, and is not repeated here.
Example III
The embodiment provides an electronic device, which comprises a memory and a processor, wherein the memory is used for storing a computer program, and the processor runs the computer program to enable the electronic device to execute the equivalent comprehensive inertia determining method of the direct-drive fan of the first embodiment.
Alternatively, the electronic device may be a server.
In addition, the embodiment of the invention also provides a computer readable storage medium, which stores a computer program, and the computer program realizes the equivalent comprehensive inertia determining method of the direct-drive fan of the first embodiment when being executed by a processor.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.

Claims (8)

1. The method for determining the equivalent comprehensive inertia of the direct-driven fan is characterized by comprising the following steps of:
acquiring the fault occurrence time of a power grid, the real-time frequency of the power grid, the initial value of the d-axis component of the current at the grid side on a phase-locked loop coordinate system and the control parameters of a direct-drive fan at the fault recovery stage; the control of the direct-driven fan when the power grid fails comprises a virtual inertia control link, a fault ride-through control link, a machine side PI control link, a phase-locked loop PI control link and a network side PI control link; the control parameters include: proportional gain of the phase-locked loop PI control link, proportional gain of q-axis current of the machine side PI control link, proportional gain of q-axis current of the network side PI control link, differential gain of the virtual inertia control link and direct current side capacitance;
determining the transient process end time of the power grid according to the real-time frequency of the power grid;
determining the total duration of the transient process according to the fault occurrence time and the transient process ending time; the transient process of the power grid comprises a fault ride-through stage and a fault recovery stage;
acquiring the time for maintaining the upper limit value of the capacitor voltage at the direct current side in the transient process;
Calculating the total fault ride-through time according to the time for maintaining the upper limit value of the direct-current side capacitor voltage in the transient process;
calculating the total fault recovery time according to the total transient process time and the total fault crossing time;
and determining the equivalent comprehensive inertia of the direct-drive fan according to the initial value of the d-axis component of the network side current on the phase-locked loop coordinate system, the control parameter, the total transient process duration, the total fault traversing duration and the total fault recovery duration.
2. The method for determining the equivalent comprehensive inertia of the direct-drive fan according to claim 1, wherein the determining the transient process end time of the power grid according to the real-time frequency of the power grid specifically comprises:
for any moment after the fault occurs, if the absolute value of the difference value between the frequency of the power grid and the reference frequency at the current moment is smaller than the frequency fluctuation threshold value, the current moment is the transient process ending moment.
3. The method for determining the equivalent comprehensive inertia of the direct-driven fan according to claim 1, wherein determining the equivalent comprehensive inertia of the direct-driven fan according to the initial value of the d-axis component of the network-side current on the phase-locked loop coordinate system, the control parameter, the transient process total duration, the fault ride-through total duration and the fault recovery total duration specifically comprises:
Calculating the equivalent inertia sum of the direct-drive fan in the fault ride-through stage according to the total fault ride-through time;
calculating the equivalent inertia combination of the direct-drive fan in the fault recovery stage according to the initial value of the d-axis component of the network side current on the phase-locked loop coordinate system, the control parameter and the total fault recovery time length;
and calculating the equivalent comprehensive inertia of the direct-drive fan according to the equivalent inertia combination of the direct-drive fan in the fault ride-through stage, the equivalent inertia combination of the direct-drive fan in the fault recovery stage and the total duration of the transient process.
4. The method for determining equivalent integrated inertia of a direct-drive fan according to claim 3, wherein the following formula is adopted to calculate the equivalent inertia combination of the direct-drive fan in the fault ride-through stage:
；
wherein ,for equivalent inertia combination of direct-drive fans in fault ride-through stage, T 2 And t is the time, which is the total fault ride-through time.
5. The method for determining equivalent integrated inertia of a direct-drive fan according to claim 3, wherein the following formula is adopted to calculate the equivalent inertia combination of the direct-drive fan in the fault recovery stage:
；
wherein ,for equivalent inertia combination of direct-drive fans in fault recovery stage, T 1 For the total time length of fault recovery, i wd0 For the initial value of d-axis component of network side current on phase-locked loop coordinate system, K p_pll Is the proportional gain, K of the phase-locked loop PI control link p1 For the proportional gain, K of the q-axis current node of the machine side PI control loop p_vdc For the proportional gain of q-axis current of the network-side PI control link, K d_vic The differential gain of the virtual inertia control link is C is the direct-current side capacitance.
6. The method for determining the equivalent integrated inertia of the direct-drive fan according to claim 3, wherein the following formula is adopted to calculate the equivalent integrated inertia of the direct-drive fan:
；
wherein ,HT Is the equivalent comprehensive inertia of the direct-drive fan,for the equivalent inertia combination of the direct-drive fan in the fault recovery stage,the equivalent inertia of the direct-drive fan in the fault ride-through stage is equal to T, which is the total duration of the transient process and T 1 For the total time length of fault recovery, T 2 Is the total duration of fault ride-through.
7. A direct-drive fan equivalent integrated inertia determination system, applied to the direct-drive fan equivalent integrated inertia determination method of any one of claims 1 to 6, characterized in that the direct-drive fan equivalent integrated inertia determination system comprises:
the data acquisition unit is used for acquiring the fault occurrence time of the power grid, the real-time frequency of the power grid, the initial value of the d-axis component of the current at the grid side on the phase-locked loop coordinate system and the control parameter of the direct-driven fan at the fault recovery stage; the control of the direct-driven fan when the power grid fails comprises a virtual inertia control link, a fault ride-through control link, a machine side PI control link, a phase-locked loop PI control link and a network side PI control link; the control parameters include: proportional gain of the phase-locked loop PI control link, proportional gain of q-axis current of the machine side PI control link, proportional gain of q-axis current of the network side PI control link, differential gain of the virtual inertia control link and direct current side capacitance;
The end time determining unit is connected with the data acquisition unit and is used for determining the transient process end time of the power grid according to the real-time frequency of the power grid;
the transient total duration determining unit is respectively connected with the data acquisition unit and the ending time determining unit and is used for determining the total duration of the transient process according to the fault occurrence time and the transient process ending time; the transient process of the power grid comprises a fault ride-through stage and a fault recovery stage;
the time length determining unit is used for obtaining the time for maintaining the upper limit value of the direct-current side capacitor voltage in the transient process and calculating the total fault crossing time length according to the time for maintaining the upper limit value of the direct-current side capacitor voltage in the transient process;
the recovery time length determining unit is respectively connected with the transient total time length determining unit and the traversing time length determining unit and is used for calculating the total fault recovery time length according to the transient process total time length and the fault traversing total time length;
the comprehensive inertia determining unit is respectively connected with the data obtaining unit, the transient total duration determining unit, the traversing duration determining unit and the recovery duration determining unit and is used for determining the equivalent comprehensive inertia of the direct-drive fan according to the initial value of the d-axis component of the network side current on the phase-locked loop coordinate system, the control parameter, the transient total duration, the fault traversing total duration and the fault recovery total duration.
8. An electronic device comprising a memory and a processor, the memory configured to store a computer program, the processor configured to execute the computer program to cause the electronic device to perform the direct drive fan equivalent integrated inertia determination method of any one of claims 1 to 6.
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CN112600199A (en) * 2020-12-07 2021-04-02 北京四方继保工程技术有限公司 Wind turbine generator equivalent rotational inertia online evaluation method based on rotor kinetic energy
CN115149577A (en) * 2022-08-09 2022-10-04 华北电力大学 Doubly-fed asynchronous wind generator transient overvoltage suppression method considering phase jump
CN115842360A (en) * 2022-08-29 2023-03-24 中国电力科学研究院有限公司 Control method and system of new energy unit

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014173131A1 (en) * 2013-04-23 2014-10-30 国家电网公司 Large power grid overall situation on-line integrated quantitative evaluation method based on response
CN112600199A (en) * 2020-12-07 2021-04-02 北京四方继保工程技术有限公司 Wind turbine generator equivalent rotational inertia online evaluation method based on rotor kinetic energy
CN115149577A (en) * 2022-08-09 2022-10-04 华北电力大学 Doubly-fed asynchronous wind generator transient overvoltage suppression method considering phase jump
CN115842360A (en) * 2022-08-29 2023-03-24 中国电力科学研究院有限公司 Control method and system of new energy unit

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