CN109256817B - Method and device for controlling direct-current micro-grid interface inverter to carry out frequency regulation - Google Patents
Method and device for controlling direct-current micro-grid interface inverter to carry out frequency regulation Download PDFInfo
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- CN109256817B CN109256817B CN201811426244.0A CN201811426244A CN109256817B CN 109256817 B CN109256817 B CN 109256817B CN 201811426244 A CN201811426244 A CN 201811426244A CN 109256817 B CN109256817 B CN 109256817B
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
Abstract
The invention discloses a method for controlling a direct current micro-grid interface inverter to carry out frequency regulation, which can determine an actual grid angular frequency value in a current power distribution network by utilizing an actual grid voltage value of the power distribution network, determine a standard direct current voltage value required to be output by the inverter by utilizing the actual grid angular frequency value after the actual grid angular frequency value is obtained, and achieve the purpose of regulating the frequency of the power distribution network by utilizing the direct current voltage value output by the inverter to be equal to the standard direct current voltage value corresponding to the actual grid angular frequency value. Therefore, by adopting the scheme, the actual direct-current voltage value of the energy storage device on the direct-current side of the direct-current microgrid controls the output voltage of the direct-current microgrid interface inverter to the power distribution network, and the purpose of adjusting the frequency of the power distribution network is achieved. In addition, the invention also discloses a device for controlling the direct-current microgrid interface inverter to carry out frequency regulation, and the effect is as above.
Description
Technical Field
The invention relates to the field of power grids, in particular to a method and a device for controlling a direct-current micro-grid interface inverter to adjust frequency.
Background
The direct-current micro-grid is a micro-grid which uses direct current to transmit and distribute electric energy, when the direct-current micro-grid works in a grid-connected mode, the direct-current micro-grid is connected with a power distribution network through an inverter so as to carry out bidirectional transmission of the electric energy, and when the direct-current micro-grid is connected with the power distribution network through the inverter, the inverter works in a controllable direct-current voltage mode so as to ensure the stability of direct-current bus voltage.
However, when the dc microgrid is connected to a power distribution grid through an inverter, the main purpose of controlling the interface inverter of the dc microgrid is to ensure the self-safe and stable operation of the dc microgrid. At present, for an inverter with a three-phase three-leg structure, the frequency of a power distribution network is not adjusted by using an energy storage device on the direct current side of a direct current microgrid, and the active power output or absorbed by a direct current microgrid interface inverter to the power distribution network has a direct relation with the frequency of the power distribution network.
Therefore, how to control the output voltage provided by the dc microgrid interface inverter to the power distribution network through the energy storage device on the dc side of the dc microgrid to adjust the frequency of the power distribution network is a problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to disclose a method and a device for controlling a direct-current microgrid interface inverter to carry out frequency regulation.
In order to achieve the above purpose, the embodiment of the invention discloses the following technical scheme:
the embodiment of the invention discloses a method for controlling a direct-current micro-grid interface inverter to carry out frequency regulation, which is applied to an inverter of a three-phase three-bridge arm structure externally connected with an L filter, and comprises the following steps:
acquiring an actual power grid voltage value of a power distribution network, an actual direct current voltage value of an energy storage device in a direct current micro-grid and an actual output current value of the inverter;
determining an actual power grid angular frequency value by using the actual power grid voltage value;
determining a standard direct-current voltage value by utilizing the actual power grid angular frequency value and a direct-current voltage rated value of the energy storage device;
calculating a voltage error value between the standard direct current voltage value and the actual direct current voltage value;
calculating an output current rating of the inverter using the voltage error value and a PI controller;
decomposing the rated output current value and the actual output current value in a dq two-phase rotating coordinate system to obtain a rated d-axis output current value, a rated q-axis output current value, an actual d-axis output current value and an actual q-axis output current value;
and modulating the rated value of the d-axis output current, the rated value of the q-axis output current, the actual output current value of the d-axis and the actual output current value of the q-axis to obtain a modulation voltage so as to regulate the frequency of the power distribution network through the modulation voltage.
Optionally, the determining a standard dc voltage value by using the actual grid angular frequency value and a dc voltage rated value of the energy storage device includes:
calculating a frequency error value between the actual power grid angular frequency value and a rated power grid frequency value;
calculating the product of the frequency error value and the virtual damping coefficient to obtain a first product value;
carrying out differential operation on the frequency error value after a first-order low-pass filtering link and multiplying the frequency error value by a virtual inertia coefficient to obtain a second product;
calculating the sum of the first product value and the second product value to obtain an error value of the direct-current voltage;
and superposing the error value of the direct current voltage and the rated value of the direct current voltage to obtain the standard direct current voltage value.
Optionally, the virtual damping coefficient is calculated by using the following formula:
wherein D is the virtual damping coefficient udc,maxIs the maximum DC voltage value udc,oFor said DC voltage nominal value, ωmaxIs the maximum grid angular frequency value, omegaoIs a nominal angular frequency value;
correspondingly, the virtual inertia coefficient is calculated by adopting the following formula:
wherein J is the virtual inertia coefficient, CdcIs the capacitance value u of the energy storage devicedcThe actual DC voltage value is obtained.
Optionally, the determining an actual grid angular frequency value by using the actual grid voltage value specifically includes:
and performing phase locking on the actual power grid voltage value by using a phase-locked loop to obtain the actual power grid angular frequency value and the actual phase angle.
Optionally, the decomposing the rated output current value and the actual output current value under the dq two-phase rotation coordinate system includes:
and converting the output current rated value and the actual output current value from an abc coordinate system to the dq two-phase rotation coordinate system by using the phase angle and decomposing.
The embodiment of the invention discloses a device for controlling a direct-current microgrid interface inverter to carry out frequency regulation, which is applied to an inverter of a three-phase three-bridge arm structure externally connected with an L filter, and comprises:
the acquisition module is used for acquiring an actual power grid voltage value of a power distribution network, an actual direct current voltage value of an energy storage device in a direct current micro-grid and an actual output current value of the inverter;
the first determination module is used for determining an actual power grid angle frequency value by using the actual power grid voltage value;
the second determining module is used for determining a standard direct-current voltage value by utilizing the actual power grid angle frequency value and a direct-current voltage rated value of the energy storage device;
the first calculation module is used for calculating a voltage error value between the standard direct-current voltage value and the actual direct-current voltage value;
a second calculation module for calculating an output current rating of the inverter using the voltage error value and a PI controller;
the decomposition module is used for decomposing the rated output current value and the actual output current value under a dq two-phase rotating coordinate system to obtain a d-axis output current rated value, a q-axis output current rated value, a d-axis actual output current value and a q-axis actual output current value;
and the modulation module is used for modulating the rated value of the d-axis output current, the rated value of the q-axis output current, the actual output current value of the d-axis and the actual output current value of the q-axis to obtain modulation voltage so as to control the frequency regulation of the power distribution network through the modulation voltage.
Optionally, the second determining module includes:
the first calculation unit is used for calculating a frequency error value between the actual power grid frequency value and a rated power grid frequency value;
the first product unit is used for calculating the product of the frequency error value and the virtual damping coefficient to obtain a first product value;
the second product unit is used for carrying out differential operation on the frequency error value after a first-order low-pass filtering link and multiplying the frequency error value by a virtual inertia coefficient to obtain a second product;
the second calculation unit is used for calculating the sum of the first product value and the second product value to obtain an error value of the direct-current voltage;
and the superposition unit is used for superposing the error value of the direct current voltage and the rated value of the direct current voltage to obtain the standard direct current voltage value.
Optionally, the first determining module includes:
and the phase locking unit is used for performing phase locking on the actual power grid voltage value by using a phase locking loop to obtain the actual power grid angular frequency value and the actual phase angle.
Optionally, the decomposition module includes:
and the decomposition unit is used for converting the output current rated value and the actual output current value from an abc coordinate system to the dq two-phase rotation coordinate system by using the phase angle and decomposing the output current rated value and the actual output current value.
Thirdly, the embodiment of the present invention discloses another apparatus for controlling a dc micro-grid interface inverter to perform frequency adjustment, which is applied to an inverter of a three-phase three-leg structure externally connected with an L filter, and includes:
a memory for storing a computer program;
a processor for executing the computer program stored in the memory to implement the steps of any of the above mentioned methods for controlling a dc microgrid interface inverter for frequency regulation.
Therefore, the method for controlling the dc microgrid interface inverter to adjust the frequency disclosed by the embodiment of the invention can determine the actual grid angular frequency value in the current power distribution network by using the actual grid voltage value of the power distribution network, and after the actual grid angular frequency value is obtained, determine the standard dc voltage value which needs to be output by the inverter by using the actual grid angular frequency value, and at this time, the dc voltage value output by the inverter needs to be equal to the standard dc voltage value corresponding to the actual grid angular frequency value, so as to achieve the purpose of adjusting the frequency of the power distribution network. Therefore, after the standard direct-current voltage value is obtained, a voltage error value between the standard direct-current voltage value and the actual direct-current voltage value of the inverter is determined, the output current rated value of the inverter is calculated by using the voltage error value, and then the decomposition quantities of the output current rated value and the actual output current value under the dq two-phase rotation coordinate system are synthesized: and modulating the decomposition values to obtain final modulation voltage, wherein the d-axis output current rated value, the q-axis output current rated value, the d-axis actual output current value and the q-axis actual output current value are the output voltage of the inverter containing the power grid angular frequency value of the power distribution network. Therefore, by adopting the scheme, the actual direct-current voltage value of the energy storage device on the direct-current side of the direct-current microgrid controls the output voltage of the direct-current microgrid interface inverter to the power distribution network, and the purpose of adjusting the frequency of the power distribution network is achieved. In addition, the embodiment of the invention also discloses a device for controlling the direct-current microgrid interface inverter to carry out frequency regulation, and the effect is as above.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a three-phase three-leg inverter externally connected with an L filter according to an embodiment of the present invention;
fig. 2 is a schematic flowchart of a method for controlling a dc microgrid interface inverter to perform frequency regulation according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a process for calculating a rated output current of an inverter according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a solving process of a modulation voltage according to an embodiment of the present invention;
fig. 5 is a flowchart illustrating a specific implementation manner of step S23 according to the embodiment of the present invention;
fig. 6 is a schematic diagram of a specific implementation process of step S23 according to the embodiment of the present invention;
fig. 7 is a schematic structural diagram of an apparatus for controlling a dc microgrid interface inverter to perform frequency adjustment according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of another apparatus for controlling a dc microgrid interface inverter to perform frequency adjustment according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a method and a device for controlling a direct-current microgrid interface inverter to carry out frequency regulation.
First, a structure of an inverter of a three-phase three-leg structure externally connected with an L filter is described in an embodiment of the present invention, please refer to fig. 1, where fig. 1 is a schematic structural diagram of a three-phase three-leg inverter of an externally connected L filter disclosed in an embodiment of the present invention, where one side of a dc micro-grid is connected with an energy storage device 10, and a voltage at the energy storage device is udcThe energy storage device 10 is connected to a three-phase three-bridge arm filter 20, the three-phase three-bridge arm filter 20 is externally connected to an L filter 30, and the L filter 30 is connected to a distribution network, wherein the actual grid voltage value of the distribution network adopts ugThe actual output current value of the three-phase three-leg filter 20 is represented by igIndicating that the actual DC voltage value of the energy storage device in the DC micro-grid is udcAnd (4) showing.
Referring to fig. 2, fig. 2 is a schematic flow chart of a method for controlling a dc microgrid interface inverter to perform frequency adjustment, the method including:
s21: and acquiring an actual power grid voltage value of the power distribution network, an actual direct current voltage value of an energy storage device in the direct current micro-grid and an actual output current value of the inverter.
When the direct-current micro-grid is connected with a power distribution network through the inverter, the interface inverter of the direct-current micro-grid is controlled to ensure the safe and stable operation of the direct-current micro-grid. At present, for an inverter with a three-phase three-leg structure, the frequency of a power distribution network is not adjusted by using an energy storage device on the direct current side of a direct current microgrid, active power output or absorbed by a direct current microgrid interface inverter to the power distribution network has a direct relation with the frequency of the power distribution network, and the active power output or absorbed by the inverter to the power distribution network can be adjusted by using the voltage at the energy storage device of the direct current microgrid interface inverter. Therefore, how to adjust the frequency of the power distribution network by using the voltage value of the energy storage side of the inverter is a technical problem mainly solved by the invention.
Specifically, in this embodiment, the actual grid voltage value of the power distribution network is ugIndicating that the actual DC voltage value of the energy storage device in the DC micro-grid is udcIndicating that the actual output current value of the inverter is igAnd (4) showing. Wherein, a voltage sensor and a current sensor can be adopted to collect ug、udcAnd ig。
S22: and determining an actual grid angle frequency value by using the actual grid voltage value.
Specifically, in this embodiment, the actual grid angular frequency value may be the actual grid voltage value u through the grid voltage phase-locked module PLLgThe phase locking is performed to obtain the actual grid angular frequency value ω and the phase angle (see the prior art in this section). In the embodiment of the invention, the actual power grid angular frequency value is represented by omega, and the phase angle is represented by theta.
S23: and determining a standard direct-current voltage value by utilizing the actual grid angular frequency value and the direct-current voltage rated value of the energy storage device.
Specifically, in this embodiment, the actual angular frequency value ω and the rated angular frequency ω exist in the power distribution network0After the actual grid angular frequency omega is obtained, the actual grid angular frequency omega is compared with the rated angular frequency omega0Obtaining a frequency error difference value delta omega after difference is made, then multiplying the actual power grid angular frequency omega by a virtual damping coefficient D, meanwhile, obtaining an error value of the direct current voltage of the direct current micro-grid after the frequency error difference value delta omega is subjected to differential operation and is multiplied by a virtual inertia coefficient J after a first-order low-pass filtering link, and superposing the products of the two parts
Thereafter using the error value of the DC voltage
Rated value u of DC voltagedc,oThe standard direct current voltage value u is obtained by superpositiondc *。
S24: and calculating a voltage error value between the standard direct current voltage value and the actual direct current voltage value.
S25: and calculating the rated value of the output current of the inverter by using the voltage error value and the PI controller.
Specifically, in the present embodiment, as for the output current of the inverter, there is an actual output current value i of the invertergAnd output current rating ig *. Step S25 is described in detail below with reference to fig. 3, where fig. 3 is a schematic diagram illustrating a process of calculating a rated output current of an inverter according to an embodiment of the present invention; the actual DC voltage value udcAnd a standard DC voltage value udc *Performing difference to obtain a DC voltage error value
Error value of DC voltage
After being input into the PI controller, the output current rated value i is obtained through the operation of the PI controllerg *。
S26: and decomposing the rated output current value and the actual output current value in a dq two-phase rotating coordinate system to obtain a d-axis output current rated value, a q-axis output current rated value, a d-axis actual output current value and a q-axis actual output current value.
Specifically, in the present embodiment, the rated output current value ig *And the actual output current value igIn the abc coordinate system, the output current nominal value i is required to be obtained in order to solve the final modulation voltageg *And the actual output current value igConverting the abc coordinate system into a dq two-phase rotating coordinate system, and setting a rated value i of the output current in the dq two-phase rotating coordinate systemg *And the actual output current value igDecomposition is carried out.
S27: and modulating the rated value of the d-axis output current, the rated value of the q-axis output current, the actual output current value of the d-axis and the actual output current value of the q-axis to obtain a modulation voltage so as to regulate the frequency of the power distribution network through the modulation voltage.
Specifically, in this embodiment, u is adopted as the modulation voltageiTo illustrate step S27 in detail, step S27 is described in detail with reference to fig. 4, and fig. 4 is a schematic diagram illustrating a solving process of a modulation voltage according to an embodiment of the present invention; wherein d-axis is output with a rated current igd *Q-axis output current nominal value igq *D-axis actual output Current value igdAnd q-axis actual output current value igqThe d-axis modulation voltage u is obtained through the operation in FIG. 4idAnd q-axis modulation voltage uiqThen modulating the d-axis with the voltage uidAnd q-axis modulation voltage uiqSynthesizing to obtain a modulation voltage ui. In FIG. 4, LfIs the inductance of the L filter, ugdAs d-axis actual grid voltage component, ugqIs the q-axis actual grid voltage component.
Therefore, the method for controlling the dc microgrid interface inverter to adjust the frequency disclosed by the embodiment of the invention can determine the actual grid angular frequency value in the current power distribution network by using the actual grid voltage value of the power distribution network, and after the actual grid angular frequency value is obtained, determine the standard dc voltage value which needs to be output by the inverter by using the actual grid angular frequency value, and at this time, the dc voltage value output by the inverter needs to be equal to the standard dc voltage value corresponding to the actual grid angular frequency value, so as to achieve the purpose of adjusting the frequency of the power distribution network. Therefore, after the standard direct-current voltage value is obtained, a voltage error value between the standard direct-current voltage value and the actual direct-current voltage value of the inverter is determined, the output current rated value of the inverter is calculated by using the voltage error value, and then the decomposition quantities of the output current rated value and the actual output current value under the dq two-phase rotation coordinate system are synthesized: and modulating the decomposition values to obtain final modulation voltage, wherein the d-axis output current rated value, the q-axis output current rated value, the d-axis actual output current value and the q-axis actual output current value are the output voltage of the inverter containing the power grid angular frequency value of the power distribution network. Therefore, by adopting the scheme, the actual direct-current voltage value of the energy storage device on the direct-current side of the direct-current microgrid controls the output voltage of the direct-current microgrid interface inverter to the power distribution network, and the purpose of adjusting the frequency of the power distribution network is achieved.
Based on the above embodiments, the present invention discloses a specific implementation example of step S23, please refer to fig. 5, fig. 5 is a flowchart illustrating a specific implementation manner of step S23 disclosed in the embodiment of the present invention, as an alternative embodiment of the present invention, step S23 specifically includes:
s231: calculating a frequency error value between the actual power grid angular frequency value and the rated power grid frequency value;
s232: calculating the product of the frequency error value and the virtual damping coefficient to obtain a first product value;
s233: carrying out differential operation on the frequency error value after a first-order low-pass filtering link and multiplying the frequency error value by a virtual inertia coefficient to obtain a second product value;
s234: calculating the sum of the first product value and the second product value to obtain the error value of the direct current voltage;
s235: and superposing the error value of the direct current voltage and the rated value of the direct current voltage to obtain a standard direct current voltage value.
Specifically, in this embodiment, the following describes the optional embodiment in detail with reference to fig. 6, please refer to fig. 6, and fig. 6 is a schematic diagram of a specific implementation process of step S23 disclosed in this embodiment of the present invention, and after obtaining the actual grid angular frequency ω and the rated angular frequency ω0Obtaining a frequency error difference value delta omega after difference making, on one hand, multiplying the delta omega by a virtual damping coefficient D, on the other hand, after the delta omega passes through a first-order low-pass filtering link (input into a low-pass filter), performing differential operation and multiplying by a virtual inertia coefficient J to obtain a straight lineError value of current voltage
Thereafter using the error value of the DC voltage
Rated value u of DC voltagedc,oThe standard direct current voltage value u is obtained by superpositiondc *. In FIG. 6, TsIs the time constant, s is the Laplace operator.
As an alternative embodiment of the present invention, the virtual damping coefficient D is specifically calculated by using the following formula:
wherein u isdc,maxIs the maximum DC voltage value udc,oFor a rated value of DC voltage, omegamaxIs the maximum grid angular frequency value, omegaoIs a nominal angular frequency value;
the maximum DC voltage value u can be determined with respect to the virtual damping coefficient Ddc,maxTaking a DC voltage rating u of 110% timesdc,oThe maximum grid angular frequency value omega is calculatedmaxTaking a nominal angular frequency value omega of 105 timeso. Specifically, the formula is shown as follows:
as an alternative embodiment of the present invention, the virtual inertia coefficient J is specifically calculated by using the following formula:
wherein, CdcIs the capacitance value u of the energy storage devicedcIs the actual dc voltage value.
Referring to fig. 7, fig. 7 is a schematic structural diagram of an apparatus for controlling a dc microgrid interface inverter to perform frequency adjustment according to an embodiment of the present invention, where the apparatus includes:
the acquiring module 701 is used for acquiring an actual power grid voltage value of a power distribution network, an actual direct current voltage value of an energy storage device in a direct current microgrid and an actual output current value of an inverter;
a first determining module 702, configured to determine an actual grid angular frequency value using the actual grid voltage value;
a second determining module 703, configured to determine a standard dc voltage value by using the actual grid angular frequency value and a dc voltage rated value of the energy storage device;
a first calculating module 704, configured to calculate a voltage error value between the standard dc voltage value and the actual dc voltage value;
a second calculation module 705 for calculating an output current rating of the inverter using the voltage error value and the PI controller;
the decomposition module 706 is configured to decompose the output current rated value and the actual output current value in a dq two-phase rotation coordinate system to obtain a d-axis output current rated value, a q-axis output current rated value, a d-axis actual output current value and a q-axis actual output current value;
and the modulation module 707 is configured to modulate the d-axis output current rated value, the q-axis output current rated value, the d-axis actual output current value, and the q-axis actual output current value to obtain a modulation voltage, so as to control frequency regulation of the power distribution network by the modulation voltage.
Therefore, the device for controlling the dc microgrid interface inverter to adjust the frequency disclosed by the embodiment of the invention can determine the actual grid angular frequency value in the current power distribution network by using the actual grid voltage value of the power distribution network, and after the actual grid angular frequency value is obtained, determine the standard dc voltage value which needs to be output by the inverter by using the actual grid angular frequency value, and at this time, the output dc voltage value of the inverter needs to be equal to the standard dc voltage value corresponding to the actual grid angular frequency value, so as to achieve the purpose of adjusting the frequency of the power distribution network. Therefore, after the standard direct-current voltage value is obtained, a voltage error value between the standard direct-current voltage value and the actual direct-current voltage value of the inverter is determined, the output current rated value of the inverter is calculated by using the voltage error value, and then the decomposition quantities of the output current rated value and the actual output current value under the dq two-phase rotation coordinate system are synthesized: and modulating the decomposition values to obtain final modulation voltage, wherein the d-axis output current rated value, the q-axis output current rated value, the d-axis actual output current value and the q-axis actual output current value are the output voltage of the inverter containing the power grid angular frequency value of the power distribution network. Therefore, by adopting the scheme, the actual direct-current voltage value of the energy storage device on the direct-current side of the direct-current microgrid controls the output voltage of the direct-current microgrid interface inverter to the power distribution network, and the purpose of adjusting the frequency of the power distribution network is achieved.
Based on the above embodiment, as a preferred embodiment, the second determining module 703 includes:
the first calculation unit is used for calculating a frequency error value between the actual power grid angle frequency value and a rated power grid frequency value;
the first product unit is used for calculating the product of the frequency error value and the virtual damping coefficient to obtain a first product value;
the second product unit is used for carrying out differential operation on the frequency error value after a first-order low-pass filtering link and multiplying the frequency error value by a virtual inertia coefficient to obtain a second product;
the second calculation unit is used for calculating the sum of the first product value and the second product value to obtain an error value of the direct-current voltage;
and the superposition unit is used for superposing the error value of the direct current voltage and the rated value of the direct current voltage to obtain the standard direct current voltage value.
Based on the above embodiment, as a preferred embodiment, the first determining module 702 includes:
and the phase locking unit is used for performing phase locking on the actual power grid voltage value by using a phase locking loop to obtain the actual power grid angular frequency value and the actual phase angle.
Based on the above embodiment, as a preferred embodiment, the decomposition module 706 includes:
and the decomposition unit is used for converting the output current rated value and the actual output current value from an abc coordinate system to the dq two-phase rotation coordinate system by using the phase angle and decomposing the output current rated value and the actual output current value.
Referring to fig. 8, fig. 8 is a schematic structural diagram of another apparatus for controlling a dc microgrid interface inverter to perform frequency adjustment according to an embodiment of the present invention, including:
a memory 801 for storing a computer program;
a processor 802 for executing the computer program stored in the memory to implement the steps of the method for controlling the dc microgrid interface inverter to perform frequency adjustment mentioned in any of the above embodiments.
Another apparatus for controlling a dc microgrid interface inverter to perform frequency adjustment disclosed in this embodiment may call a computer program stored in a memory through a processor to implement the steps of the method for controlling a dc microgrid interface inverter to perform frequency adjustment disclosed in any one of the above embodiments, so the apparatus has the same practical effects as the above method for controlling a dc microgrid interface inverter to perform frequency adjustment.
A method and an apparatus for controlling a dc microgrid interface inverter to perform frequency regulation disclosed in the present application are described in detail above. The principles and embodiments of the present application are explained herein using specific examples, which are provided only to help understand the method and the core idea of the present application. It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present application without departing from the principle of the present application, and such improvements and modifications also fall within the scope of the claims of the present application.
The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
Claims (8)
1. A method for controlling a direct current micro-grid interface inverter to carry out frequency regulation is applied to an inverter of a three-phase three-bridge arm structure externally connected with an L filter, and is characterized by comprising the following steps:
acquiring an actual power grid voltage value of a power distribution network, an actual direct current voltage value of an energy storage device in a direct current micro-grid and an actual output current value of the inverter;
determining an actual power grid angular frequency value by using the actual power grid voltage value;
determining a standard direct-current voltage value by utilizing the actual power grid angular frequency value and a direct-current voltage rated value of the energy storage device;
determining the standard dc voltage value comprises:
the actual power grid angular frequency value is differenced with the rated power grid angular frequency value to obtain a frequency error difference value; multiplying the actual grid angular frequency value by a virtual damping coefficient to obtain a first product; the frequency error difference value is subjected to a first-order low-pass filtering link, then subjected to differential operation and multiplied by a virtual inertia coefficient to obtain a second product; superposing the first product and the second product to obtain an error value of the direct-current voltage of the direct-current microgrid; superposing the error value of the direct current voltage and the rated value of the direct current voltage to obtain the standard direct current voltage value;
calculating a voltage error value between the standard direct current voltage value and the actual direct current voltage value;
calculating an output current rating of the inverter using the voltage error value and a PI controller;
for the rated value and actual output current value of the output current
Decomposing under a two-phase rotating coordinate system to obtain
Rated value of shaft output current,
Rated value of shaft output current,
Actual output current value of shaft and
the actual output current value of the shaft;
to the above
Rated value of shaft output current, the
Rated value of shaft output current, the
The actual output current value of the shaft and
and modulating the actual output current value of the shaft to obtain a modulation voltage so as to adjust the frequency of the power distribution network through the modulation voltage.
2. The method according to claim 1, wherein the virtual damping coefficient is calculated by using the following formula:
wherein the content of the first and second substances,
is the virtual damping coefficient,
Is the maximum DC voltage value,
Is the rated value of the DC voltage,
Is the maximum grid angular frequency value,
Is a nominal angular frequency value;
correspondingly, the virtual inertia coefficient is calculated by adopting the following formula:
wherein the content of the first and second substances,
is the virtual inertia coefficient,
Is the capacitance value of the energy storage device,
The actual DC voltage value is obtained.
3. The method according to claim 1, wherein the determining an actual grid angular frequency value using the actual grid voltage value specifically comprises:
and performing phase locking on the actual power grid voltage value by using a phase-locked loop to obtain the actual power grid angular frequency value and the actual phase angle.
4. The method of claim 3, wherein the nominal and actual output current values are at
The decomposition under the biphase rotating coordinate system comprises the following steps:
using the phase angle to combine the output current nominal value and the actual output current value
The coordinate system is converted to
Biphase rotates the coordinate system and decomposes.
5. The utility model provides a device for controlling little electric wire netting interface inverter of direct current carries out frequency control, is applied to the inverter of the three-phase three-leg structure of external L wave filter, its characterized in that includes:
the acquisition module is used for acquiring an actual power grid voltage value of a power distribution network, an actual direct current voltage value of an energy storage device in a direct current micro-grid and an actual output current value of the inverter;
the first determination module is used for determining an actual power grid angle frequency value by using the actual power grid voltage value;
the second determining module is used for determining a standard direct-current voltage value by utilizing the actual power grid angle frequency value and a direct-current voltage rated value of the energy storage device;
the second determining module is specifically configured to make a difference between the actual grid angular frequency value and a rated grid angular frequency value to obtain a frequency error difference value; multiplying the actual grid angular frequency value by a virtual damping coefficient to obtain a first product; the frequency error difference value is subjected to a first-order low-pass filtering link, then subjected to differential operation and multiplied by a virtual inertia coefficient to obtain a second product; superposing the first product and the second product to obtain an error value of the direct-current voltage of the direct-current microgrid; superposing the error value of the direct current voltage and the rated value of the direct current voltage to obtain the standard direct current voltage value;
the first calculation module is used for calculating a voltage error value between the standard direct-current voltage value and the actual direct-current voltage value;
a second calculation module for calculating an output current rating of the inverter using the voltage error value and a PI controller;
a decomposition module for comparing the rated value of the output current with the actual value of the output current
Decomposing under a two-phase rotating coordinate system to obtain
Rated value of shaft output current,
Rated value of shaft output current,
Actual output current value of shaft and
the actual output current value of the shaft;
a modulation module for modulating the signal
Rated value of shaft output current, the
Shaft transmissionRated value of the output current, said
The actual output current value of the shaft and
and modulating the actual output current value of the shaft to obtain a modulation voltage so as to control the frequency regulation of the power distribution network through the modulation voltage.
6. The apparatus of claim 5, wherein the first determining module comprises:
and the phase locking unit is used for performing phase locking on the actual power grid voltage value by using a phase locking loop to obtain the actual power grid angular frequency value and the actual phase angle.
7. The apparatus of claim 6, wherein the decomposition module comprises:
a decomposition unit for using the phase angle to combine the output current nominal value and the actual output current value
The coordinate system is converted to
Biphase rotates the coordinate system and decomposes.
8. The utility model provides a device for controlling little electric wire netting interface inverter of direct current carries out frequency control, is applied to the inverter of the three-phase three-leg structure of external L wave filter, its characterized in that includes:
a memory for storing a computer program;
a processor for executing a computer program stored in the memory to implement the steps of the method for controlling a dc microgrid interface inverter to perform frequency regulation according to any one of claims 1 to 4.
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