CN116191452B - Current control method, device, equipment and storage medium under low voltage fault - Google Patents

Current control method, device, equipment and storage medium under low voltage fault Download PDF

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Publication number
CN116191452B
CN116191452B CN202310173203.XA CN202310173203A CN116191452B CN 116191452 B CN116191452 B CN 116191452B CN 202310173203 A CN202310173203 A CN 202310173203A CN 116191452 B CN116191452 B CN 116191452B
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current
target
voltage
quadrature
direct
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CN116191452A (en
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何大清
芦清
周旭
唐仲霖
傅文波
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Chint Group R & D Center Shanghai Co ltd
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Chint Group R & D Center Shanghai Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • 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
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • 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
    • 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
    • H02J2300/40—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Eletrric Generators (AREA)

Abstract

The invention provides a current control method, a device, equipment and a storage medium under low-voltage faults, which are used for controlling the current of an inverter based on a virtual synchronous generator; the method comprises the following steps: acquiring a current power grid voltage direct axis component, a current power grid voltage quadrature axis component and a target direct axis current and a target quadrature axis current when a preset low voltage fault occurs; the target direct current is less than the target quadrature current; determining a current rotor power angle and determining a current excitation voltage; determining target impedance and target inductance according to the target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle; and controlling the current of the inverter according to the target impedance and the target inductance. Low voltage ride through of the inverter exhibiting voltage source characteristics is achieved; secondly, the power grid voltage sampling points are not required to be considered, so that the applicability is improved; finally, related circuits are not required to be additionally added, and hardware cost is reduced.

Description

Current control method, device, equipment and storage medium under low voltage fault
Technical Field
The invention relates to the technical field of inverters, in particular to a current control method, a device, equipment and a storage medium under low-voltage faults.
Background
The grid may be affected by the power supply and load and appear unstable. In the distributed power system, the energy storage or the power generation system with the energy storage function can play a role in supporting a power grid, the occurrence of the unstable state can be reduced by the energy storage, and particularly, stronger adaptability can be shown for a weak power grid. To achieve this goal, however, power electronics will play a critical role. The current-variable capability and the high controllability of the power electronic device are key to ensuring the stable operation of the weak current network. The inverter is used as a connecting device of energy and a power grid, has high controllability and can provide guarantee for the safety of the power grid and the high-efficiency work of new energy.
In order to solve the influence of weak grid impedance on the inverter, various targeted measures are researched and applied, so that the inverter can realize low-voltage ride through when low-voltage faults occur. If the grid voltage is sampled on the filter capacitor, the influence of the grid impedance on the current is eliminated by purposefully designing a current controller, but the method is an inverter for LCL filtering, and the grid voltage sampling point of the inverter is arranged on the capacitor C instead of a common joint (PCC), so that the inverter has larger limitation; in the multi-terminal direct current, the fluctuation of the detected direct current voltage is utilized to change the output of the direct current power, so that the grid-connected side has better damping performance, but an additional direct current power control circuit is needed, and the hardware cost is increased; as for the inverter exhibiting the current source characteristic, the crossover can be realized by using the clipping link of the current, but cannot be applied to the inverter exhibiting the voltage source characteristic by adopting the control method of the virtual synchronous generator.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a current control method, a device, equipment and a storage medium under low-voltage faults.
In a first aspect, in one embodiment, the present invention provides a method for controlling current in a low voltage fault, the method comprising controlling current in an inverter based on a virtual synchronous generator; the method comprises the following steps:
acquiring a current power grid voltage direct axis component, a current power grid voltage quadrature axis component and a target direct axis current and a target quadrature axis current when a preset low voltage fault occurs; the target direct current is less than the target quadrature current;
determining a current rotor power angle of the virtual synchronous generator and determining a current excitation voltage of the virtual synchronous generator;
determining target impedance and target inductance of the virtual synchronous generator according to the target direct current, the target quadrature current, the current exciting voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle;
determining a target impedance and a target inductive reactance of the virtual synchronous generator according to the target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle, comprising:
Obtaining target impedance and target inductance according to the target direct current, the target quadrature current, the current exciting voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle through the following formulas;
wherein I is dref Is a direct axis current, I qref For quadrature axis current, E f For exciting voltage, U d U is the direct axis component of the power grid voltage q Delta is a rotor power angle, R is impedance, and X is inductance;
and replacing the initial impedance and the initial inductance according to the target impedance and the target inductance to realize current control of the inverter.
In one embodiment, the target direct current is zero and the target quadrature current is the nominal current; determining a target impedance and a target inductive reactance of the virtual synchronous generator according to the target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle, comprising:
obtaining the target impedance of the virtual synchronous generator to be zero based on the target straight shaft current;
and determining the target inductive reactance of the virtual synchronous generator according to the target impedance, the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle.
In one embodiment, determining the target impedance and the target inductive reactance of the virtual synchronous generator based on the target direct current, the target quadrature current, the present excitation voltage, the present grid voltage direct component, the present grid voltage quadrature component, and the present rotor power angle comprises:
obtaining target impedance and target inductance according to the target direct current, the target quadrature current, the current exciting voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle through the following formulas;
wherein I is dref Is a direct axis current, I qref For quadrature axis current, E f For exciting voltage, U d U is the direct axis component of the power grid voltage q The power grid voltage quadrature component is represented by delta, a rotor power angle, R, impedance and inductance.
In one embodiment, determining the current rotor power angle includes:
acquiring current rotational inertia, current rotor angular velocity, current control active power, current scheduling active power, current frequency droop coefficient, current power grid rated angular velocity, current power grid angular velocity and current damping coefficient;
and determining the current rotor power angle according to the current moment of inertia, the current rotor angular velocity, the current control active power, the current scheduling active power, the current frequency droop coefficient, the current power grid rated angular velocity, the current power grid angular velocity and the current damping coefficient.
In one embodiment, determining the current rotor power angle based on the current moment of inertia, the current rotor angular velocity, the current control active power, the current scheduled active power, the current frequency droop coefficient, the current grid rated angular velocity, the current grid angular velocity, and the current damping coefficient includes:
obtaining a current rotor power angle through the following formula according to the current moment of inertia, the current rotor angular velocity, the current control active power, the current dispatching active power, the current frequency droop coefficient, the current power grid rated angular velocity, the current power grid angular velocity and the current damping coefficient;
wherein J is moment of inertia, ω VSG For rotor angular velocity, P * To control active power, P ref To schedule active power, K d As frequency droop coefficient omega * For the rated angular speed, omega of the electric network g The power grid angular velocity is represented by D, the damping coefficient is represented by delta, the rotor power angle is represented by delta, and the first order derivative is represented by delta.
In one embodiment, determining the current excitation voltage includes:
acquiring current power grid output power and current power grid voltage;
and determining the current excitation voltage according to the current rotor power angle, the current power grid output power and the current power grid voltage.
In one embodiment, determining the present excitation voltage based on the present rotor power angle, the present grid output power, and the present grid voltage includes:
According to the current rotor power angle, the current power grid output power and the current power grid voltage, the current excitation voltage is obtained through the following formula;
wherein P is the output power of the power grid, E f For exciting voltage, U g The power grid voltage, R is impedance, X is inductance, and delta is rotor power angle.
In a second aspect, in one embodiment, the present invention provides a current control apparatus for controlling current of an inverter based on a virtual synchronous generator in a low voltage fault; the device comprises:
the parameter acquisition module is used for acquiring the current power grid voltage direct-axis component, the current power grid voltage quadrature-axis component and the target direct-axis current and the target quadrature-axis current when the preset low voltage faults; the target direct current is less than the target quadrature current;
the parameter determining module is used for determining the current rotor power angle of the virtual synchronous generator and determining the current excitation voltage of the virtual synchronous generator;
the armature determining module is used for determining target impedance and target inductive reactance of the virtual synchronous generator according to the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current power grid voltage direct-axis component, the current power grid voltage quadrature-axis component and the current rotor power angle;
The armature determination module is specifically configured to obtain a target impedance and a target inductive reactance according to a target direct current, a target quadrature current, a current excitation voltage, a current grid voltage direct component, a current grid voltage quadrature component and a current rotor power angle through the following formulas;
wherein I is dref Is a direct axis current, I qref For quadrature axis current, E f For exciting voltage, U d U is the direct axis component of the power grid voltage q Delta is a rotor power angle, R is impedance, and X is inductance;
and the current control module is used for replacing the initial impedance and the initial inductance according to the target impedance and the target inductance so as to realize the current control of the inverter.
In a third aspect, in one embodiment, the invention provides a computer device comprising a memory and a processor; the memory stores a computer program, and the processor is configured to execute the computer program in the memory to perform the steps in the current control method under the low voltage fault in any of the embodiments described above.
In a fourth aspect, in one embodiment, the present invention provides a storage medium storing a computer program to be loaded by a processor to perform the steps in the current control method under a low voltage fault in any of the above embodiments.
According to the current control method, the device, the equipment and the storage medium under the low-voltage fault, aiming at the inverter which adopts the control method of the virtual synchronous generator and presents the voltage source characteristic, the target direct-axis current and the target quadrature-axis current which are expected to be achieved in the low-voltage fault are preset, so that when the low-voltage fault occurs, the current grid-voltage direct-axis component, the current grid-voltage quadrature-axis component and the target direct-axis current and the target quadrature-axis current in the preset low-voltage fault are obtained, the current rotor power angle is determined, the current exciting voltage is determined, the reverse deduction is carried out according to the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid-voltage direct-axis component and the current rotor power angle, the required target impedance and the target inductive reactance are determined, and finally the current control is carried out based on the target impedance and the target inductive reactance, so that the obtained actual direct-axis current and the actual quadrature-axis current are respectively identical with the target direct-axis current and the target quadrature-axis current, and the requirement of low-voltage ride through is met; low voltage ride through of the inverter exhibiting voltage source characteristics is achieved; secondly, the power grid voltage sampling points are not required to be considered, so that the applicability is improved; finally, related circuits are not required to be additionally added, and hardware cost is reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of an application scenario of a current control method under a low voltage fault in an embodiment of the present invention;
FIG. 2 is a flow chart of a current control method under low voltage fault in an embodiment of the invention;
FIG. 3 is a schematic diagram of an energy storage system according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a control flow of a virtual synchronous generator according to an embodiment of the present invention;
FIG. 5a is a graph showing the variation waveforms of the direct current command, the quadrature current command and the grid power under control 1 according to one embodiment of the present invention;
FIG. 5b is a graph showing the variation waveforms of the direct current command, the quadrature current command and the grid power under control 2 according to one embodiment of the present invention;
FIG. 6a is a waveform diagram showing the angular velocity and power variation of the rotor under control 1 according to one embodiment of the present invention;
FIG. 6b is a waveform diagram showing the angular velocity and power variation of the rotor under control 2 according to one embodiment of the present application;
FIG. 7a is a graph showing voltage and current variation at a common junction under control 1 according to one embodiment of the present application;
FIG. 7b is a graph showing voltage and current variation at the common junction under control 2 according to one embodiment of the present application;
FIG. 8 is a schematic diagram of a current control device under low voltage fault in an embodiment of the present application;
fig. 9 is a schematic diagram showing an internal structure of a computer device according to an embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to fall within the scope of the application.
In the description of the present application, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more of the described features. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise. In the present application, the term "exemplary" is used to mean "serving as an example, instance, or illustration. Any embodiment described as "exemplary" in this disclosure is not necessarily to be construed as preferred or advantageous over other embodiments. The following description is presented to enable any person skilled in the art to make and use the application. In the following description, details are set forth for purposes of explanation. It will be apparent to one of ordinary skill in the art that the present application may be practiced without these specific details. In other instances, well-known structures and processes have not been described in detail so as not to obscure the description of the application with unnecessary detail. Thus, the present application is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
The current control method under the low-voltage fault is applied to the current control device under the low-voltage fault, and the current control device under the low-voltage fault is arranged in the computer equipment; the computer device may be a terminal, for example, a mobile phone or a tablet computer, and the computer device may also be a server, or a service cluster formed by a plurality of servers.
As shown in fig. 1, fig. 1 is a schematic diagram of an application scenario of a current control method under a low voltage fault in an embodiment of the present invention, where the application scenario of the current control method under a low voltage fault in the embodiment of the present invention includes a computer device 100 (a current control device under a low voltage fault is integrated in the computer device 100), and a computer readable storage medium corresponding to the current control method under the low voltage fault is run in the computer device 100 to execute steps of the current control method under the low voltage fault.
It can be understood that the computer device in the application scenario of the current control method under the low voltage fault shown in fig. 1, or the apparatus included in the computer device, does not limit the embodiments of the present invention, that is, the number of devices and the type of devices included in the application scenario of the current control method under the low voltage fault, or the number of apparatuses and the type of apparatuses included in each device do not affect the overall implementation of the technical solution in the embodiments of the present invention, and may be calculated as equivalent replacement or derivation of the technical solution claimed in the embodiments of the present invention.
The computer device 100 in the embodiment of the present invention may be an independent device, or may be a device network or a device cluster formed by devices, for example, the computer device 100 described in the embodiment of the present invention includes, but is not limited to, a computer, a network host, a single network device, a plurality of network device sets, or a cloud device formed by a plurality of devices. Wherein, cloud equipment is composed of a large number of computers or network equipment based on Cloud Computing (Cloud Computing).
It will be understood by those skilled in the art that the application scenario shown in fig. 1 is only one application scenario corresponding to the technical solution of the present invention, and does not limit the application scenario of the technical solution of the present invention, other application scenarios may also include more or fewer computer devices than those shown in fig. 1, or a network connection relationship of the computer devices, for example, only 1 computer device is shown in fig. 1, and it may be understood that the scenario of the current control method under the low voltage fault may also include one or more other computer devices, which is not limited herein in particular; a memory may also be included in the computer device 100 for storing information related to the current control method in the event of a low voltage fault.
In addition, in the application scenario of the current control method under the low voltage fault in the embodiment of the present invention, the computer device 100 may be provided with a display device, or the computer device 100 is not provided with a display device and is connected to the external display device 200 in a communication manner, where the display device 200 is used to output the result of executing the current control method under the low voltage fault in the computer device. The computer device 100 may access a background database 300 (the background database 300 may be a local memory of the computer device 100, and the background database 300 may also be disposed in the cloud), where the background database 300 stores information related to a current control method under a low voltage fault.
It should be noted that, the application scenario of the current control method under the low voltage fault shown in fig. 1 is merely an example, and the application scenario of the current control method under the low voltage fault described in the embodiment of the present invention is for more clearly describing the technical solution of the embodiment of the present invention, and does not constitute a limitation to the technical solution provided by the embodiment of the present invention.
Based on the application scenario of the current control method under the low-voltage fault, an embodiment of the current control method under the low-voltage fault is provided.
In a first aspect, as shown in fig. 2, in one embodiment, the present invention provides a current control method under a low voltage fault, which performs current control on an inverter based on a virtual synchronous generator; the method comprises the following steps:
step 201, obtaining a current grid voltage direct axis component, a current grid voltage quadrature axis component and a target direct axis current and a target quadrature axis current when a preset low voltage fault occurs;
the target direct-axis current is smaller than the target quadrature-axis current, and the target current difference between the target direct-axis current and the target quadrature-axis current is larger than the preset current difference;
the low-voltage fault is a typical fault of a power grid (especially a weak power grid), which requires that the inverter not only has low-voltage ride-through capability, but also requires the supporting capability of the power grid during ride-through, and particularly, the inverter outputs reactive current as much as possible when the low-voltage fault occurs, and the direct-axis current corresponds to active current, and the quadrature-axis current corresponds to reactive current, namely, when preset, the target quadrature-axis current is made larger as much as possible, and the target direct-axis current is made smaller; therefore, in the present embodiment, in order to achieve this object, the target current difference between the target straight axis current and the target quadrature axis current may be made larger than the preset current difference;
The magnitude of the preset current difference depends on the power grid (such as a weak power grid or not), and the preset current difference is larger compared with the conventional power grid; the execution main body of the current control method under the low-voltage fault in the embodiment is a virtual synchronous generator control module in the inverter;
the power grid voltage is decomposed into a component on a direct axis (namely a d axis) and a component on a quadrature axis (namely a q axis) through a phase-locked loop in the inverter, and the direct axis component and the quadrature axis component of the current power grid voltage can be obtained by detecting the output condition of the current phase-locked loop;
the target direct-axis current and the target quadrature-axis current are preset, and the target current meeting the low-voltage crossing requirement under the low-voltage fault can be understood as the expected output under the low-voltage fault in the virtual synchronous generator control method;
step 202, determining a current rotor power angle of the virtual synchronous generator and determining a current excitation voltage of the virtual synchronous generator;
the rotor is a virtual rotor of the inverter under the control method of the virtual synchronous generator, and the rotor power angle can be obtained by calculating various parameters of the inverter and the power grid parameters; in the embodiment, the current parameters of the inverter and the current power grid parameters can be detected in real time, so that the current rotor power angle is obtained by calculation according to the parameters; in other embodiments, for example, in a specific case, when each parameter of the inverter and the power grid parameter do not change, the rotor power angle can be defaulted to be a fixed value, so that the current rotor power angle can be directly preset based on the scene, and the current rotor power angle can be directly read when the method needs to be executed;
The exciting voltage can be obtained by calculating the rotor power angle, various parameters of the inverter and the power grid parameters; in this embodiment, current parameters of the inverter, the rotor power angle and current power grid parameters can be detected in real time, so that the current excitation voltage is obtained by calculation according to the parameters; in other embodiments, for example, in a specific case, when each parameter of the inverter and the power grid parameter do not change, the rotor power angle can be defaulted to be a fixed value, so that the excitation voltage can be further defaulted to be a fixed value, and the current excitation voltage can be directly preset based on the scene, and the method can be directly read when the method is required to be executed;
step 203, determining a target impedance and a target inductive reactance of the virtual synchronous generator according to the target direct current, the target quadrature current, the current exciting voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle;
the impedance and the inductive reactance refer to the impedance and the inductive reactance of a virtual armature of the inverter under the control method of the virtual synchronous generator;
in the traditional control flow of the virtual synchronous generator, the direct-axis current is taken as a dependent variable, and depends on the dependent variables such as exciting voltage, grid voltage direct-axis component, grid voltage quadrature-axis component, rotor power angle, impedance, inductance and the like; similarly, the quadrature axis current is taken as a dependent variable, and depends on the dependent variables such as exciting voltage, grid voltage direct axis component, grid voltage quadrature axis component, rotor power angle, impedance, inductance and the like;
In this embodiment, since the corresponding target direct current and target quadrature current are preset, the direct current and the quadrature current are no longer used as dependent variables, and at this time, the impedance and the inductance can be used as dependent variables, and the target impedance and the target inductance required for outputting the target direct current and the target quadrature current in the current scene are determined according to the obtained and determined target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle;
step 204, current control is carried out on the inverter according to the target impedance and the target inductance;
under the control method of the virtual synchronous generator, current control is executed under the traditional condition, the impedance and the inductive reactance of the virtual armature have preset initial impedance and initial inductive reactance, and then the first direct current and the first quadrature current which are actually output are determined according to the initial impedance, the initial inductive reactance, the obtained and determined current excitation voltage, current power grid voltage direct axis component, current power grid voltage quadrature axis component and current rotor power angle; in this embodiment, after the target impedance and the target inductance are obtained, the initial impedance and the initial inductance are replaced, and the resetting of the impedance and the inductance is completed, so that when the current control is performed, the second direct-axis current and the second quadrature-axis current which are actually output can be determined according to the target impedance, the target inductance, the obtained and determined current excitation voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle, and the second direct-axis current and the second quadrature-axis current are respectively equal to the preset target direct-axis current and the preset target quadrature-axis current;
The initial impedance and the initial inductance are used for realizing current control under normal conditions, so that the same requirements are set according to actual control requirements; the filter inductance of the inverter is related to a strong power grid, the internal resistance of the strong power grid is small, the current harmonic wave of the inverter is easy to be absorbed, the internal resistance of the weak power grid is large, larger current harmonic wave is generated, the voltage and the current are mutually influenced, the harmonic wave voltage enters a control system through voltage feedforward, and high-frequency oscillation is easy to generate; the introduced virtual resistor (namely corresponding to the initial impedance) can enhance the resonance damping of the lc filter and reduce the oscillation, so that the initial impedance is properly increased and the higher harmonic wave can be effectively reduced;
wherein, although the damping effect is stronger as the initial impedance is larger, the upper limit value of the initial impedance is as follows in order to keep the control loop stable(L is the filter inductance, ts is the sampling period), while for weak grid scenarios, the initial impedance may be set to be slightly greater than the filter inductance actual value;
the current control method under the low voltage fault in the embodiment is executed after the low voltage fault occurs in the power grid, the voltage fault is judged in a voltage detection mode, namely, the power grid voltage of a half cycle is continuously detected, whether the power grid has the voltage fault or not is determined according to the change of the power grid voltage of the half cycle, the judgment of the low voltage fault is needed to be carried out according to a local power grid rule and according to a voltage standard for stopping active power output, and therefore whether the low voltage fault occurs or not is determined, if yes, the method is executed;
After the grid voltage is recovered, namely, no low-voltage fault exists, the target impedance and the target inductive reactance are replaced by the original initial impedance and the original inductive reactance.
According to the current control method under the low voltage fault, aiming at the inverter which adopts the control method of the virtual synchronous generator and presents the voltage source characteristic, the target direct-axis current and the target quadrature-axis current which are expected to be achieved in the low voltage fault are preset, so that when the low voltage fault occurs, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the preset target direct-axis current and target quadrature-axis current in the low voltage fault are obtained, the current rotor power angle and the current exciting voltage are determined, reverse deduction is carried out according to the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle, the required target impedance and target inductive reactance are determined, and finally, the current control is carried out based on the target impedance and the target inductive reactance, so that the obtained actual direct-axis current and the actual quadrature-axis current are respectively identical with the target direct-axis current and the target quadrature-axis current, and the preset target quadrature-axis current, and the requirements of low voltage ride through are met; low voltage ride through of the inverter exhibiting voltage source characteristics is achieved; secondly, the power grid voltage sampling points are not required to be considered, so that the applicability is improved; finally, related circuits are not required to be additionally added, and hardware cost is reduced.
In one embodiment, the target direct current is zero and the target quadrature current is the nominal current; determining a target impedance and a target inductive reactance of the virtual synchronous generator according to the target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle, comprising:
obtaining the target impedance of the virtual synchronous generator to be zero based on the target straight shaft current;
the above embodiment has mentioned that the target current difference between the target direct current and the target quadrature current may be made larger than the preset current difference, so as to meet the requirement of outputting reactive current as much as possible; in this embodiment, the target direct-axis current may be directly set to zero, and the target quadrature-axis current may be set to the rated current (i.e., the allowable maximum current), so as to maximize the target current difference between the target direct-axis current and the target quadrature-axis current, so as to meet the current requirement of the serious low-voltage fault;
wherein, according to the relation of the direct axis current and the impedance, when the target direct axis current is set to zero, the target impedance can be directly determined to be zero;
determining a target inductive reactance of the virtual synchronous generator according to the target impedance, the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle;
When the target impedance is unknown, multiple groups of target impedance and target inductive reactance (mainly depending on the functional relation among the parameters) may be determined according to the target direct-axis current, the target quadrature-axis current, the current excitation voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle; in this embodiment, the target impedance is already predetermined, so that a unique target inductance can be obtained finally;
during the low-voltage fault, as the actually output straight-axis current is the target straight-axis current with zero, the active power is converted into the rotor kinetic energy, the rotor rotating speed is increased, the kinetic energy on the rotor is increased, after the low-voltage fault is eliminated, all parameters are restored to the initial values, and the rotor kinetic energy is released, so that the output of the active power is quickly restored.
In one embodiment, determining the target impedance and the target inductance from the target direct current, the target quadrature current, the present excitation voltage, the present grid voltage direct component, the present grid voltage quadrature component, and the present rotor power angle comprises:
obtaining target impedance and target inductance through formula 1 according to the target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle;
Formula 1:
wherein I is dref Is a direct axis current, I qref For quadrature axis current, E f For exciting voltage, U d U is the direct axis component of the power grid voltage q Delta is a rotor power angle, R is impedance, and X is inductance;
wherein, as can be seen from the above symbols, the direct axis current I dref And quadrature axis current I qref The current command is actually a current command corresponding to the current parameter, and the current command is used for being output to a current control loop of the inverter;
wherein, under the weak current network scene, the power grid voltage quadrature axis component U q The current power grid voltage quadrature component is a component which is greatly interfered, and the target of the current power grid voltage quadrature component under the control of the phase-locked loop is zero, so that the obtained current power grid voltage quadrature component is also zero under ideal conditions; thereby converting the above formula 1 into formula 2;
formula 2:
the current control loop in the inverter respectively controls the direct-axis current and the quadrature-axis current, the output end is added with a grid voltage direct-axis component and a grid voltage quadrature-axis component as feedforward, and in the same way, in order to avoid the interference of the quadrature-axis component, only the direct-axis component is feedforward in a weak grid scene;
when the target direct current is set to zero and the target quadrature current is set to the rated current, the formula 2 can be converted into the formula 3;
formula 3:
wherein I is rate Is rated current;
Wherein, the above formula 3 is simplified to obtain formula 4;
formula 4:
wherein, since the target impedance can be directly set to zero, the above equation 4 can be further converted into equation 5;
formula 5: e (E) f ＝U d +X·I rate ；
Wherein, by sorting the above formula 5 and combining a predetermined target impedance, formula 6 representing the target impedance and the target inductance can be obtained;
formula 6:
in one embodiment, determining the current rotor power angle includes:
acquiring current rotational inertia, current rotor angular velocity, current control active power, current scheduling active power, current frequency droop coefficient, current power grid rated angular velocity, current power grid angular velocity and current damping coefficient;
determining a current rotor power angle according to the current moment of inertia, the current rotor angular velocity, the current control active power, the current scheduling active power, the current frequency droop coefficient, the current power grid rated angular velocity, the current power grid angular velocity and the current damping coefficient;
wherein the active power, i.e. the mechanical power, is controlled and the active power, i.e. the given power, is scheduled.
In one embodiment, determining the current rotor power angle based on the current moment of inertia, the current rotor angular velocity, the current control active power, the current scheduled active power, the current frequency droop coefficient, the current grid rated angular velocity, the current grid angular velocity, and the current damping coefficient includes:
Obtaining a current rotor power angle through 7 according to the current moment of inertia, the current rotor angular velocity, the current control active power, the current dispatching active power, the current frequency droop coefficient, the current power grid rated angular velocity, the current power grid angular velocity and the current damping coefficient;
formula 7:
wherein J is moment of inertia, ω VSG For rotor angular velocity, P * To control active power, P ref To schedule active power, K d As frequency droop coefficient omega * For the rated angular speed, omega of the electric network g The angular speed of the power grid is represented by D, a damping coefficient is represented by delta, and delta is the rotor power angle;
wherein, according to the symbol, the active power P is controlled * Scheduling active power P ref The actual active power instructions correspond to different types of active power;
wherein, formula 7 is the equation of motion of the rotor;
in order to make the embodiment clearer, an excitation control equation, a kinetic energy equation output by the rotor and a direct current side energy storage equation of the inverter corresponding to the rotor energy are provided; the excitation control equation is shown as a formula 8, the kinetic energy equation of the rotor output is shown as a formula 9, and the energy storage equation of the rotor energy corresponding to the DC side of the inverter is shown as a formula 10;
formula 8: q (Q) * ＝Q ref -K q (U * -U g )；
Wherein Q is * For reactive power control, Q ref For reactive power scheduling, K q As voltage sag factor, U * For rated voltage of electric network, U g Is the grid voltage;
formula 9:
wherein K is D A coefficient of energy consumption for the damping system;
wherein ω is considered at steady state VSG ＝ω g The energy consumption of the damping system is 0, and the larger moment of inertia J is more beneficial to system stability; when in dynamic state, the damping system plays a role in inhibiting frequency offset, and a larger damping parameter D is beneficial to eliminating frequency fluctuation;
formula 10:
wherein C is DC Is a direct current capacitor, V DC Is a direct current voltage;
wherein the energy storage system is arranged at the direct current side, thereby guaranteeing energy output, namely maintaining V DC Constant. For a weak power grid, larger J and D are designed to be beneficial to the stability of the power grid, but the energy is sourced from a direct current side, the state of an energy storage system and the direct current capacitance parameters determine the speed and the size of energy output, and the J and D are set to be matched with the speed and the size of the energy output;
in one embodiment, determining the current excitation voltage includes:
acquiring current power grid output power and current power grid voltage;
and determining the current excitation voltage according to the current rotor power angle, the current power grid output power and the current power grid voltage.
In one embodiment, determining the present excitation voltage based on the present rotor power angle, the present grid output power, and the present grid voltage includes:
Obtaining a current excitation voltage according to a current rotor power angle, a current power grid output power and a current power grid voltage through a formula 11;
formula 11:
wherein P is the output power of the power grid, E f For exciting voltage, U g The power grid voltage, R is impedance, X is inductance, delta is rotor power angle;
from equation 11, the excitation voltage E f Also related to the impedance and inductance, so based on equation 11, the actual resulting present excitation voltage is an expression of the target impedance and target inductance, rather thanSpecific values.
In one embodiment, to make the technical solution of the above embodiment clearer, an exemplary embodiment is provided, as shown in fig. 3, and a 125kVA energy storage system is provided, where a three-level architecture (NPC) is adopted;
wherein, the main parameters of the energy storage system are shown in table 1;
TABLE 1
Wherein, as shown in fig. 4, a control flow of a virtual synchronous generator control module (i.e., VSG) is provided;
all the control details in fig. 4 may find corresponding parts in the above embodiments, and are not described herein again;
wherein the symbols of FIG. 4, which do not find the corresponding parts in the above embodiment, are described herein, the part symbols include the mechanical torque T m Battery torque T e Angle phase theta VSG Grid phase theta g ；
Wherein, as can be seen from fig. 3 and 4, the VSG converts the command into mechanical torque, and converts the mechanical torque into a voltage source by utilizing the electromechanical conversion principle; the current instruction can be obtained by calculating the interrelation between the voltage source and the power grid; after the current command enters the current control loop, outputting a voltage value, superposing the direct axis component of the power grid voltage to become a voltage modulation command, and finally generating voltage in a pulse form; the current control loop is conventional control and will not be described here;
the inverter works under the steady state that the active power output is 1pu, the PCC point of the inverter generates a ground fault at 5s, and the fault is relieved at 5.2 s; two control modes are adopted here: control 1 did not change any parameters; the control 2 changes the setting of the impedance and the inductance according to the mode 6 after the low-voltage fault occurs, and recovers the impedance and the inductance after the low-voltage fault is relieved; simulating the two control modes;
wherein, as shown in fig. 5a and 5b, the direct axis current command I under two control modes is obtained dref Quadrature axis current command I qref And a varying waveform of grid power P; as can be seen from fig. 5a and 5b, since the impedance of control 1 is not zero, under the action of the active command, I dref After the fault is over, more jitter appears in the recovery process of each parameter, and the control flow is proved to enter the limiting link more; control 2 after the impedance is zero, I dref Rapidly jumping to 0, and rapidly jumping back to the original value after the fault is over; the recovery of the active output is faster, and although the active output has certain overshoot, the jitter in the transient variation is less, so that the control parameter design is proved to be more reasonable;
as shown in fig. 6a and 6b, rotor angular velocity and power angle variation waveforms in two control modes are obtained; as can be seen from fig. 6a and 6b, the angular velocity and the power angle of the control 1 fluctuate more at the steady-state point, which proves that the rotor releases all kinetic energy at low voltage, and after the fault is over, the process of absorbing power from the outside and releasing is completed; the angular speed and the power angle of the control 2 are basically changed at the same side, so that the rotor is proved to convert the power into the kinetic energy, and the kinetic energy is released after the fault is over, and therefore, the recovery speed of the active output is faster;
as shown in fig. 7a and 7b, voltage Ua, ub, uc and current Ia, ib, ic variation waveforms of the PCC in two control modes are obtained; it can be seen from fig. 7a and 7b that the voltage and current variations of the weak grid affect each other, the fluctuation amplitude of control 1 in voltage recovery is slightly larger than that of control 2, and the current variation of control 2 is also smoother than that of control 1.
In a second aspect, as shown in fig. 8, in one embodiment, the present invention provides a current control apparatus for controlling current of an inverter based on a virtual synchronous generator in a low voltage fault; the device comprises:
The parameter obtaining module 301 is configured to obtain a current grid voltage direct axis component, a current grid voltage quadrature axis component, and a target direct axis current and a target quadrature axis current when a preset low voltage fault occurs; the target direct current is less than the target quadrature current;
a parameter determination module 302 for determining a current rotor power angle of the virtual synchronous generator and determining a current excitation voltage of the virtual synchronous generator;
the armature determination module 303 is configured to determine a target impedance and a target inductive reactance of the virtual synchronous generator according to the target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component, and the current rotor power angle;
the current control module 304 is configured to perform current control on the inverter according to the target impedance and the target inductance.
Through the current control device under the low voltage fault, aiming at the inverter which adopts the control method of the virtual synchronous generator and presents the voltage source characteristic, the target direct-axis current and the target quadrature-axis current which are expected to be achieved in the low voltage fault are preset, so that when the low voltage fault occurs, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the target direct-axis current and the target quadrature-axis current which are preset in the low voltage fault are obtained, the current rotor power angle is determined, the current exciting voltage is determined, reverse deduction is carried out according to the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle, the required target impedance and the target inductive reactance are determined, and finally, the current control is carried out based on the target impedance and the target inductive reactance, so that the obtained actual direct-axis current and the actual quadrature-axis current are respectively identical with the target direct-axis current and the target quadrature-axis current, and the requirements of low voltage ride through are met; low voltage ride through of the inverter exhibiting voltage source characteristics is achieved; secondly, the power grid voltage sampling points are not required to be considered, so that the applicability is improved; finally, related circuits are not required to be additionally added, and hardware cost is reduced.
In one embodiment, the target direct current is zero and the target quadrature current is the nominal current; the armature determination module is specifically used for obtaining zero target impedance of the virtual synchronous generator based on the target straight shaft current; and determining the target inductive reactance of the virtual synchronous generator according to the target impedance, the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle.
In one embodiment, the armature determination module is specifically configured to obtain the target impedance and the target inductive reactance according to the target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component, and the current rotor power angle through the following formula;
wherein I is dref Is a direct axis current, I qref For quadrature axis current, E f For exciting voltage, U d U is the direct axis component of the power grid voltage q The power grid voltage quadrature component is represented by delta, a rotor power angle, R, impedance and inductance.
In one embodiment, the parameter determination module includes:
the power angle determining module is used for obtaining current rotational inertia, current rotor angular velocity, current control active power, current scheduling active power, current frequency sagging coefficient, current power grid rated angular velocity, current power grid angular velocity and current damping coefficient; and determining the current rotor power angle according to the current moment of inertia, the current rotor angular velocity, the current control active power, the current scheduling active power, the current frequency droop coefficient, the current power grid rated angular velocity, the current power grid angular velocity and the current damping coefficient.
In one embodiment, the power angle determining module is specifically configured to obtain the current rotor power angle according to the current moment of inertia, the current rotor angular velocity, the current control active power, the current scheduling active power, the current frequency droop coefficient, the current power grid rated angular velocity, the current power grid angular velocity, and the current damping coefficient through the following formula;
wherein J is moment of inertia, ω VSG For rotor angular velocity, P * To control active power, P ref To schedule active power, K d As frequency droop coefficient omega * For the rated angular speed, omega of the electric network g The power grid angular velocity is represented by D, the damping coefficient is represented by delta, the rotor power angle is represented by delta, and the first order derivative is represented by delta.
In one embodiment, the parameter determination module includes:
the voltage determining module is used for obtaining the current power grid output power and the current power grid voltage; and determining the current excitation voltage according to the current rotor power angle, the current power grid output power and the current power grid voltage.
In one embodiment, the voltage determining module is specifically configured to obtain the current excitation voltage according to the current rotor power angle, the current power grid output power and the current power grid voltage through the following formula;
wherein P is the output power of the power grid, E f For exciting voltage, U g The power grid voltage, R is impedance, X is inductance, and delta is rotor power angle.
In a third aspect, in one embodiment, the present invention provides a computer device, which is the virtual synchronous generator control module in the above embodiment, as shown in fig. 9, which shows a structure of the computer device according to the present invention, in particular:
the computer device may include one or more processors 401 of a processing core, memory 402 of one or more computer readable storage media, a power supply 403, and an input unit 404, among other components. Those skilled in the art will appreciate that the architecture of the computer device shown in fig. 9 is not limiting of the computer device, and may include more or fewer components than shown, or may combine certain components, or a different arrangement of components. Wherein:
the processor 401 is a control center of the computer device, connects various parts of the entire computer device using various interfaces and lines, and performs various functions of the computer device and processes data by running or executing software programs and/or modules stored in the memory 402, and calling data stored in the memory 402, thereby performing overall monitoring of the computer device. Optionally, processor 401 may include one or more processing cores; preferably, the processor 401 may integrate an application processor and a modem processor, wherein the application processor mainly processes an operating system, a user interface, a computer program, etc., and the modem processor mainly processes wireless communication. It will be appreciated that the modem processor described above may not be integrated into the processor 401.
The memory 402 may be used to store software programs and modules, and the processor 401 executes various functional applications and data processing by executing the software programs and modules stored in the memory 402. The memory 402 may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, a computer program (such as a sound playing function, an image playing function, etc.) required for at least one function, and the like; the storage data area may store data created according to the use of the server, etc. In addition, memory 402 may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other volatile solid-state storage device. Accordingly, the memory 402 may also include a memory controller to provide the processor 401 with access to the memory 402.
The computer device further comprises a power supply 403 for supplying power to the various components, preferably the power supply 403 may be logically connected to the processor 401 by a power management system, so that functions of charge, discharge, and power consumption management may be performed by the power management system. The power supply 403 may also include one or more of any of a direct current or alternating current power supply, a recharging system, a power failure detection circuit, a power converter or inverter, a power status indicator, and the like.
The computer device may also include an input unit 404, which input unit 404 may be used to receive input numeric or character information and to generate keyboard, mouse, joystick, optical or trackball signal inputs related to user settings and function control.
Although not shown, the computer device may further include a display unit or the like, which is not described herein. In particular, in this embodiment, when the computer device trains the computer device for the model, the processor 401 in the computer device loads executable files corresponding to the processes of one or more computer programs into the memory 402 according to the following instructions, and the processor 401 executes the computer programs stored in the memory 402 to perform the following steps:
acquiring a current power grid voltage direct axis component, a current power grid voltage quadrature axis component and a target direct axis current and a target quadrature axis current when a preset low voltage fault occurs; the target direct current is less than the target quadrature current;
determining a current rotor power angle of the virtual synchronous generator and determining a current excitation voltage of the virtual synchronous generator;
determining target impedance and target inductance of the virtual synchronous generator according to the target direct current, the target quadrature current, the current exciting voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle;
And controlling the current of the inverter according to the target impedance and the target inductance.
Through the computer equipment, aiming at the inverter which adopts the control method of the virtual synchronous generator and presents the voltage source characteristic, the target direct-axis current and the target quadrature-axis current which are expected to be achieved when the low-voltage fault occurs are preset, so that when the low-voltage fault occurs, the current grid-voltage direct-axis component, the current grid-voltage quadrature-axis component and the target direct-axis current and the target quadrature-axis current when the preset low-voltage fault occur are obtained, the current rotor power angle and the current exciting voltage are determined, reverse deduction is carried out according to the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid-voltage direct-axis component, the current grid-voltage quadrature-axis component and the current rotor power angle, the required target impedance and target inductive reactance are determined, and finally, the current control is carried out based on the target impedance and the target inductive reactance, so that the obtained actual direct-axis current and the obtained actual quadrature-axis current are respectively identical with the target direct-axis current and the target quadrature-axis current, and the requirements of low-voltage ride through are met; low voltage ride through of the inverter exhibiting voltage source characteristics is achieved; secondly, the power grid voltage sampling points are not required to be considered, so that the applicability is improved; finally, related circuits are not required to be additionally added, and hardware cost is reduced.
It will be appreciated by those of ordinary skill in the art that all or part of the steps of any of the methods of the above embodiments may be performed by a computer program, or by computer program control related hardware, which may be stored in a computer readable storage medium and loaded and executed by a processor.
In a fourth aspect, in one embodiment, the present invention provides a storage medium having stored therein a plurality of computer programs, the computer programs being loadable by a processor, to perform the steps of:
acquiring a current power grid voltage direct axis component, a current power grid voltage quadrature axis component and a target direct axis current and a target quadrature axis current when a preset low voltage fault occurs; the target direct current is less than the target quadrature current;
determining a current rotor power angle of the virtual synchronous generator and determining a current excitation voltage of the virtual synchronous generator;
determining target impedance and target inductance of the virtual synchronous generator according to the target direct current, the target quadrature current, the current exciting voltage, the current grid voltage direct component, the current grid voltage quadrature component and the current rotor power angle;
and controlling the current of the inverter according to the target impedance and the target inductance.
Through the storage medium, aiming at the inverter which adopts the control method of the virtual synchronous generator and presents the voltage source characteristic, target direct-axis current and target quadrature-axis current which are expected to be achieved when the low-voltage fault occurs are preset, so that when the low-voltage fault occurs, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the target direct-axis current and the target quadrature-axis current which are preset when the low-voltage fault occurs are obtained, the current rotor power angle is determined, the current exciting voltage is determined, reverse deduction is carried out according to the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle, the required target impedance and target inductive reactance are determined, and finally, the current control is carried out based on the target impedance and the target inductive reactance, so that the obtained actual direct-axis current and the obtained actual quadrature-axis current are respectively identical with the target direct-axis current and the target quadrature-axis current, and the requirements of low-voltage ride through are met; low voltage ride through of the inverter exhibiting voltage source characteristics is achieved; secondly, the power grid voltage sampling points are not required to be considered, so that the applicability is improved; finally, related circuits are not required to be additionally added, and hardware cost is reduced.
It will be appreciated by those of ordinary skill in the art that any reference to memory, storage, database, or other medium used in the embodiments provided herein may include non-volatile and/or volatile memory. The nonvolatile memory can include Read Only Memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink), DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), among others.
The steps of the method for controlling current under low voltage fault in any embodiment provided by the present invention can be executed by the computer program stored in the storage medium, so that the beneficial effects of the method for controlling current under low voltage fault in any embodiment provided by the present invention can be achieved, which are detailed in the previous embodiments and are not described herein.
The specific implementation of each operation above may be referred to the previous embodiments, and will not be described herein.
In the foregoing embodiments, the descriptions of the embodiments are focused on, and the portions of one embodiment that are not described in detail in the foregoing embodiments may be referred to in the foregoing detailed description of other embodiments, which are not described herein again.
The foregoing has described in detail the method, apparatus, device and storage medium for controlling current in low voltage fault provided by the present invention, and specific examples have been applied herein to illustrate the principles and embodiments of the present invention, and the above description of the examples is only for helping to understand the method and core idea of the present invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in light of the ideas of the present invention, the present description should not be construed as limiting the present invention.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

Claims (9)

1. The current control method under the low-voltage fault is characterized in that the current control is carried out on the inverter based on the virtual synchronous generator; the method comprises the following steps:
acquiring a current power grid voltage direct axis component, a current power grid voltage quadrature axis component and a target direct axis current and a target quadrature axis current when a preset low voltage fault occurs; the target direct current is less than the target quadrature current;
determining a current rotor power angle of the virtual synchronous generator and determining a current excitation voltage of the virtual synchronous generator;
determining target impedance and target inductive reactance of the virtual synchronous generator according to the target direct-axis current, the target quadrature-axis current, the current excitation voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle;
the determining the target impedance and the target inductive reactance of the virtual synchronous generator according to the target direct-axis current, the target quadrature-axis current, the current excitation voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle includes:
obtaining the target impedance and the target inductive reactance according to the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current power grid voltage direct-axis component, the current power grid voltage quadrature-axis component and the current rotor power angle through the following formulas;
Wherein I is dref Is a direct axis current, I qref For quadrature axis current, E f For exciting voltage, U d U is the direct axis component of the power grid voltage q Delta is a rotor power angle, R is impedance, and X is inductance;
and replacing the initial impedance and the initial inductance according to the target impedance and the target inductance so as to realize current control of the inverter.
2. The method according to claim 1, wherein the target direct-axis current is zero and the target quadrature-axis current is a rated current; the determining the target impedance and the target inductive reactance of the virtual synchronous generator according to the target direct-axis current, the target quadrature-axis current, the current excitation voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle includes:
obtaining a target impedance of the virtual synchronous generator to be zero based on the target straight shaft current; and determining the target inductive reactance of the virtual synchronous generator according to the target impedance, the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle.
3. The method of current control under low voltage fault of claim 1, wherein said determining the present rotor power angle comprises:
acquiring current rotational inertia, current rotor angular velocity, current control active power, current scheduling active power, current frequency droop coefficient, current power grid rated angular velocity, current power grid angular velocity and current damping coefficient;
and determining the current rotor power angle according to the current moment of inertia, the current rotor angular speed, the current control active power, the current scheduling active power, the current frequency droop coefficient, the current power grid rated angular speed, the current power grid angular speed and the current damping coefficient.
4. A method of current control under low voltage fault as claimed in claim 3, wherein said determining said current rotor power angle from said current moment of inertia, said current rotor angular velocity, said current control active power, said current scheduled active power, said current frequency droop factor, said current grid rated angular velocity, said current grid angular velocity, and said current damping factor comprises:
Obtaining the current rotor power angle according to the current moment of inertia, the current rotor angular velocity, the current control active power, the current scheduling active power, the current frequency droop coefficient, the current power grid rated angular velocity, the current power grid angular velocity and the current damping coefficient through the following formulas;
wherein J is moment of inertia, ω VSG For rotor angular velocity, P * To control active power, P ref To schedule active power, K d As frequency droop coefficient omega * For the rated angular speed, omega of the electric network g The power grid angular velocity is represented by D, the damping coefficient is represented by delta, the rotor power angle is represented by delta, and the first order derivative is represented by delta.
5. The method for current control under a low voltage fault according to claim 1, wherein said determining the present excitation voltage comprises:
acquiring current power grid output power and current power grid voltage;
and determining the current excitation voltage according to the current rotor power angle, the current power grid output power and the current power grid voltage.
6. The method for controlling current in low voltage fault as claimed in claim 5, wherein,
the determining the current excitation voltage according to the current rotor power angle, the current power grid output power and the current power grid voltage comprises the following steps:
Obtaining the current excitation voltage according to the current rotor power angle, the current power grid output power and the current power grid voltage through the following formula;
wherein P is the output power of the power grid, E f For exciting voltage, U g The power grid voltage, R is impedance, X is inductance, and delta is rotor power angle.
7. A current control device under a low-voltage fault, characterized in that the current control is performed on an inverter based on a virtual synchronous generator; the device comprises:
the parameter acquisition module is used for acquiring the current power grid voltage direct-axis component, the current power grid voltage quadrature-axis component and the target direct-axis current and the target quadrature-axis current when the preset low voltage faults; the target direct current is less than the target quadrature current;
the parameter determining module is used for determining the current rotor power angle of the virtual synchronous generator and determining the current excitation voltage of the virtual synchronous generator;
the armature determining module is used for determining target impedance and target inductive reactance of the virtual synchronous generator according to the target direct-axis current, the target quadrature-axis current, the current exciting voltage, the current grid voltage direct-axis component, the current grid voltage quadrature-axis component and the current rotor power angle;
The armature determination module is specifically configured to obtain the target impedance and the target inductive reactance according to the target direct current, the target quadrature current, the current excitation voltage, the current grid voltage direct component, the current grid voltage quadrature component, and the current rotor power angle through the following formulas;
wherein I is dref Is a direct axis current, I qref For quadrature axis current, E f For exciting voltage, U d U is the direct axis component of the power grid voltage q Delta is a rotor power angle, R is impedance, and X is inductance;
and the current control module is used for replacing the initial impedance and the initial inductance according to the target impedance and the target inductance so as to realize the current control of the inverter.
8. A computer device comprising a memory and a processor; the memory stores a computer program, and the processor is configured to execute the computer program in the memory to perform the steps in the current control method under the low voltage fault as claimed in any one of claims 1 to 6.
9. A storage medium storing a computer program to be loaded by a processor to perform the steps in the current control method under a low voltage fault as claimed in any one of claims 1 to 6.
CN202310173203.XA 2023-02-24 2023-02-24 Current control method, device, equipment and storage medium under low voltage fault Active CN116191452B (en)

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CN111416393A (en) * 2020-04-15 2020-07-14 上海电力大学 Virtual synchronous generator fault current suppression method based on self-adaptive virtual impedance
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Publication number Priority date Publication date Assignee Title
CN111416393A (en) * 2020-04-15 2020-07-14 上海电力大学 Virtual synchronous generator fault current suppression method based on self-adaptive virtual impedance
CN114513010A (en) * 2021-08-30 2022-05-17 正泰集团研发中心(上海)有限公司 Power control method, device, electronic equipment and readable storage medium

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