CN115549098A - Current harmonic control method, device and system and computer readable storage medium - Google Patents
Current harmonic control method, device and system and computer readable storage medium Download PDFInfo
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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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
- H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
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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
- H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks
Abstract
The invention discloses a current harmonic control method, a device, a system and a computer readable storage medium, wherein the method comprises the following steps: when the fact that the power grid unbalance degree meets the preset condition is determined, obtaining a bus capacitor voltage value of a grid-connected inverter, and determining a target fundamental wave frequency harmonic wave according to the bus capacitor voltage value; and determining input current according to the target fundamental frequency harmonic, and inputting the input current into the grid-connected inverter to obtain output current. According to the method, when the unbalance degree of the power grid is determined to meet the preset condition, the target fundamental wave frequency harmonic wave is determined according to the bus capacitor voltage value of the grid-connected inverter, and then the input current is determined according to the target fundamental wave frequency harmonic wave, so that the harmonic wave of the input current of the grid-connected inverter can be suppressed, the harmonic distortion of the output current of the grid-connected inverter is reduced, and the harmonic distortion of the output current is ensured to meet the standard.
Description
Technical Field
The invention relates to the technical field of power grid control, in particular to a current harmonic control method, a current harmonic control device, a current harmonic control system and a computer readable storage medium.
Background
The unbalanced distribution of three-phase loads in the power grid, the unbalanced impedance of the power transmission line and the like can cause the unbalanced voltage of the power grid; under the condition of unbalanced power grid, the output current of the inverter can be distorted; due to the requirement for cost reduction, the capacitance value of a direct-current bus capacitor in the conventional inverter is generally small, and is more easily influenced by unbalanced fluctuation of a power grid, so that serious harmonic distortion exists in the output current of the inverter, and the whole equipment can be burned out in serious conditions. Therefore, how to reduce the harmonic distortion of the output current of the inverter is an urgent problem to be solved.
Disclosure of Invention
The invention mainly aims to provide a current harmonic control method, a current harmonic control device, a current harmonic control system and a computer readable storage medium, and aims to solve the problem of reducing harmonic distortion of output current of an inverter.
In order to achieve the above object, the present invention provides a current harmonic control method, including the steps of:
when the fact that the power grid unbalance degree meets the preset condition is determined, obtaining a bus capacitor voltage value of a grid-connected inverter, and determining a target fundamental wave frequency harmonic wave according to the bus capacitor voltage value;
and determining input current according to the target fundamental frequency harmonic, and inputting the input current into the grid-connected inverter to obtain output current.
Optionally, when it is determined that the power grid imbalance degree meets a preset condition, before the step of obtaining a bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic according to the bus capacitor voltage value, the method includes:
acquiring a u-phase voltage, a v-phase voltage and a w-phase voltage of a power grid, and calculating a balance degree effective value according to the u-phase voltage, the v-phase voltage and the w-phase voltage;
calculating the unbalance degree of the power grid according to the effective balance degree value, the u-phase voltage, the v-phase voltage and the w-phase voltage;
and determining whether the power grid unbalance degree meets a preset condition or not according to the power grid unbalance degree and a preset unbalance threshold value.
Optionally, the step of calculating the imbalance of the power grid according to the effective balance value, the u-phase voltage, the v-phase voltage and the w-phase voltage includes:
according to the balance degree effective value, the u-phase voltage, the v-phase voltage and the w-phase voltage, calculating a u-phase voltage unbalance degree, a v-phase voltage unbalance degree and a w-phase voltage unbalance degree respectively;
and comparing the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree, determining the maximum unbalance degree, and determining the power grid unbalance degree according to the maximum unbalance degree.
Optionally, the step of obtaining the bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic according to the bus capacitor voltage value includes:
acquiring the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculating the difference value of the positive bus capacitor voltage value and the negative bus capacitor voltage value;
and inputting the difference value into a controller of the grid-connected inverter, and outputting a target fundamental frequency harmonic wave according to the difference value through the controller.
Optionally, the step of obtaining the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter includes:
acquiring a capacitance value of a positive bus capacitor and a capacitance value of a negative bus capacitor of the grid-connected inverter;
determining an impedance value of a positive bus capacitor according to the capacitance value of the positive bus capacitor, and determining a voltage value of the positive bus capacitor according to the impedance value of the positive bus capacitor;
and determining the impedance value of the negative bus capacitor according to the capacitance value of the negative bus capacitor, and determining the voltage value of the negative bus capacitor according to the impedance value of the negative bus capacitor.
Optionally, the step of outputting, by the controller, a target fundamental frequency harmonic according to the difference includes:
and acquiring an initial fundamental frequency harmonic through the controller, and adjusting the amplitude and the phase of the initial fundamental frequency harmonic according to the difference value to obtain and output a target fundamental frequency harmonic.
Optionally, the step of determining an input current from the target fundamental frequency harmonic comprises:
determining a target voltage value according to the target fundamental frequency harmonic, and determining a pre-input current according to the target voltage value;
and acquiring a preset inhibiting current, and determining an input current according to the preset inhibiting current and the preset input current.
Optionally, the step of determining the pre-input current according to the target voltage value comprises:
and inputting the target voltage value into a conversion module of the grid-connected inverter, and calculating a pre-input current through the conversion module according to the target voltage value and a preset transfer function.
Optionally, after the step of determining an input current according to the target fundamental frequency harmonic and inputting the input current to the grid-connected inverter to obtain an output current, the method includes:
determining an output voltage value according to the output current machine, and calculating the utilization rate of the output voltage;
and if the utilization rate of the output voltage is lower than a preset utilization rate threshold value, adjusting the voltage value of the bus capacitor according to a preset rule.
In addition, to achieve the above object, the present invention also provides a current harmonic control apparatus including:
the determining module is used for acquiring a bus capacitor voltage value of the grid-connected inverter when the unbalance degree of the power grid is determined to meet a preset condition, and determining a target fundamental frequency harmonic wave according to the bus capacitor voltage value;
and the input module is used for determining input current according to the target fundamental frequency harmonic and inputting the input current into the grid-connected inverter to obtain output current.
Further, the determining module is further configured to:
acquiring a u-phase voltage, a v-phase voltage and a w-phase voltage of a power grid, and calculating a balance degree effective value according to the u-phase voltage, the v-phase voltage and the w-phase voltage;
calculating the unbalance degree of the power grid according to the effective balance degree value, the u-phase voltage, the v-phase voltage and the w-phase voltage;
and determining whether the power grid unbalance degree meets a preset condition or not according to the power grid unbalance degree and a preset unbalance threshold value.
Further, the determining module is further configured to:
according to the balance degree effective value, the u-phase voltage, the v-phase voltage and the w-phase voltage, respectively calculating a u-phase voltage unbalance degree, a v-phase voltage unbalance degree and a w-phase voltage unbalance degree;
and comparing the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree, determining the maximum unbalance degree, and determining the power grid unbalance degree according to the maximum unbalance degree.
Further, the determining module is further configured to:
acquiring the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculating the difference value of the positive bus capacitor voltage value and the negative bus capacitor voltage value;
and inputting the difference value into a controller of the grid-connected inverter, and outputting a target fundamental frequency harmonic wave according to the difference value through the controller.
Further, the determining module is further configured to:
acquiring a capacitance value of a positive bus capacitor and a capacitance value of a negative bus capacitor of the grid-connected inverter;
determining an impedance value of a positive bus capacitor according to the capacitance value of the positive bus capacitor, and determining a voltage value of the positive bus capacitor according to the impedance value of the positive bus capacitor;
and determining the impedance value of the negative bus capacitor according to the capacitance value of the negative bus capacitor, and determining the voltage value of the negative bus capacitor according to the impedance value of the negative bus capacitor.
Further, the determining module is further configured to:
and acquiring an initial fundamental frequency harmonic through the controller, and adjusting the amplitude and the phase of the initial fundamental frequency harmonic according to the difference value to obtain and output a target fundamental frequency harmonic.
Further, the input module is further configured to:
determining a target voltage value according to the target fundamental frequency harmonic, and determining a pre-input current according to the target voltage value;
and acquiring a preset inhibiting current, and determining an input current according to the preset inhibiting current and the preset input current.
Further, the input module is further configured to:
and inputting the target voltage value into a conversion module of the grid-connected inverter, and calculating a pre-input current through the conversion module according to the target voltage value and a preset transfer function.
Further, the input module further comprises an adjustment module, the adjustment module is configured to:
determining an output voltage value according to the output current machine, and calculating the utilization rate of the output voltage;
and if the utilization rate of the output voltage is lower than a preset utilization rate threshold value, adjusting the voltage value of the bus capacitor according to a preset rule.
In addition, to achieve the above object, the present invention also provides a current harmonic control system including: a memory, a processor, and a current harmonic control program stored on the memory and executable on the processor, the current harmonic control program when executed by the processor implementing the steps of the current harmonic control method as described above.
In addition, to achieve the above object, the present invention also provides a computer readable storage medium having stored thereon a current harmonic control program, which when executed by a processor, implements the steps of the current harmonic control method as described above.
According to the current harmonic control method provided by the invention, when the unbalance degree of a power grid is determined to meet a preset condition, a bus capacitor voltage value of a grid-connected inverter is obtained, and a target fundamental frequency harmonic is determined according to the bus capacitor voltage value; and determining input current according to the target fundamental frequency harmonic, and inputting the input current into the grid-connected inverter to obtain output current. According to the method, when the unbalance degree of the power grid is determined to meet the preset condition, the target fundamental wave frequency harmonic wave is determined according to the bus capacitor voltage value of the grid-connected inverter, and then the input current is determined according to the target fundamental wave frequency harmonic wave, so that the harmonic wave of the input current of the grid-connected inverter can be inhibited, the harmonic distortion of the output current of the grid-connected inverter is reduced, and the harmonic distortion of the output current is ensured to meet the standard.
Drawings
FIG. 1 is a schematic diagram of an apparatus architecture of a hardware operating environment according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart illustrating a first embodiment of a current harmonic control method according to the present invention;
FIG. 3 is a schematic diagram of a three-phase multi-level grid-connected inverter structure according to the present invention;
FIG. 4 is a schematic diagram of the current harmonic control process of the present invention;
FIG. 5 is a schematic flow chart illustrating a current harmonic control method according to a second embodiment of the present invention;
FIG. 6 is a flow chart illustrating a third embodiment of a current harmonic control method according to the present invention;
FIG. 7 is a schematic structural diagram of a current harmonic control apparatus according to the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, fig. 1 is a schematic device structure diagram of a hardware operating environment according to an embodiment of the present invention.
The device of the embodiment of the invention can be a PC or a server device.
As shown in fig. 1, the apparatus may include: a processor 1001, such as a CPU, a network interface 1004, a user interface 1003, a memory 1005, a communication bus 1002. The communication bus 1002 is used to implement connection communication among these components. The user interface 1003 may include a Display screen (Display), an input unit such as a Keyboard (Keyboard), and the optional user interface 1003 may also include a standard wired interface, a wireless interface. The network interface 1004 may optionally include a standard wired interface, a wireless interface (e.g., WI-FI interface). The memory 1005 may be a high-speed RAM memory or a non-volatile memory (e.g., a magnetic disk memory). The memory 1005 may alternatively be a storage device separate from the processor 1001.
Those skilled in the art will appreciate that the configuration of the apparatus shown in fig. 1 is not intended to be limiting and may include more or fewer components than those shown, or some components may be combined, or a different arrangement of components.
As shown in fig. 1, the memory 1005, which is a kind of computer storage medium, may include therein an operating system, a network communication module, a user interface module, and a current harmonic control program.
The operating system is a program for managing and controlling the portable storage device and software resources, and supports the operation of a network communication module, a user interface module, a current harmonic control program and other programs or software; the network communication module is used for managing and controlling the network interface 1002; the user interface module is used to manage and control the user interface 1003.
In the storage device shown in fig. 1, the storage device calls a current harmonic control program stored in a memory 1005 through a processor 1001 and performs operations in various embodiments of the current harmonic control method described below.
Based on the hardware structure, the embodiment of the current harmonic control method is provided.
Referring to fig. 2, fig. 2 is a schematic flow chart of a first embodiment of a current harmonic control method according to the present invention, the method including:
step S10, when the unbalance degree of the power grid is determined to meet a preset condition, acquiring a bus capacitor voltage value of the grid-connected inverter, and determining a target fundamental frequency harmonic according to the bus capacitor voltage value;
and S20, determining input current according to the target fundamental frequency harmonic, and inputting the input current into the grid-connected inverter to obtain output current.
The current harmonic control method is applied to a current harmonic control system in a power grid, and the current harmonic control system can be applied to intelligent equipment such as terminal equipment and pc terminals; for convenience of description, a current harmonic control system is taken as an example for explanation; the method comprises the steps that a current harmonic control system judges whether the power grid unbalance degree corresponding to a power grid connected with a grid-connected inverter meets a preset condition or not in the working process of the grid-connected inverter, obtains a bus capacitor voltage value of the grid-connected inverter when the fact that the power grid unbalance degree meets the preset condition is confirmed, wherein the bus capacitor voltage value comprises a positive bus capacitor voltage value and a negative bus capacitor voltage value, and calculates the difference value of the positive bus capacitor voltage value and the negative bus capacitor voltage value; the current harmonic control system inputs the difference value into a controller of the grid-connected inverter, and the controller outputs the target fundamental frequency harmonic according to the difference value; the current harmonic control system determines a target voltage value according to the target fundamental frequency harmonic and determines a pre-input current according to the target voltage value; the current harmonic control system obtains a preset suppression current, determines an input current according to the preset suppression current and a preset input current, and inputs the input current into the grid-connected inverter, so that the grid-connected inverter obtains an output current according to the input current.
According to the current harmonic control method, when the unbalance degree of the power grid is determined to meet the preset condition, the voltage value of the bus capacitor of the grid-connected inverter is obtained, and the target fundamental frequency harmonic is determined according to the voltage value of the bus capacitor; and determining input current according to the target fundamental frequency harmonic, and inputting the input current into the grid-connected inverter to obtain output current. According to the method, when the unbalance degree of the power grid is determined to meet the preset condition, the target fundamental wave frequency harmonic wave is determined according to the bus capacitor voltage value of the grid-connected inverter, and then the input current is determined according to the target fundamental wave frequency harmonic wave, so that the harmonic wave of the input current of the grid-connected inverter can be suppressed, the harmonic distortion of the output current of the grid-connected inverter is reduced, and the harmonic distortion of the output current is ensured to meet the standard.
The respective steps will be described in detail below:
step S10, when the unbalance degree of the power grid is determined to meet a preset condition, acquiring a bus capacitor voltage value of the grid-connected inverter, and determining a target fundamental frequency harmonic according to the bus capacitor voltage value;
in the embodiment, the current harmonic control system acquires a three-phase voltage corresponding to a power grid connected with the grid-connected inverter in the working process of the grid-connected inverter, determines the degree of unbalance of the power grid according to the three-phase voltage, and judges whether the degree of unbalance of the power grid meets a preset condition; when the current harmonic control system determines that the power grid unbalance degree meets the preset condition, the bus capacitor voltage value of the grid-connected inverter is obtained, and the target fundamental wave frequency harmonic is determined according to the bus capacitor voltage value. It should be noted that, the preset condition is that the power grid unbalance is greater than the unbalance threshold, and the unbalance threshold may be determined according to an actual situation, which is not limited herein; and when the current harmonic control system determines that the power grid unbalance degree does not accord with the preset condition, inputting the input current into the grid-connected inverter according to normal logic to obtain the output current.
Specifically, the step of obtaining a bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic according to the bus capacitor voltage value includes:
step S101, acquiring a positive bus capacitor voltage value and a negative bus capacitor voltage value of a grid-connected inverter, and calculating a difference value of the positive bus capacitor voltage value and the negative bus capacitor voltage value;
in the step, when the current harmonic control system determines that the power grid unbalance degree meets a preset condition, acquiring a bus capacitor voltage value of the grid-connected inverter, wherein the bus capacitor voltage value comprises a positive bus capacitor voltage value and a negative bus capacitor voltage value, and calculating a difference value between the positive bus capacitor voltage value and the negative bus capacitor voltage value; as shown in fig. 3, fig. 3 is a schematic structural diagram of a three-phase multi-level grid-connected inverter, a positive bus capacitor voltage value and a negative bus capacitor voltage value obtained by a current harmonic control system are respectively voltage values of a capacitor C1 and a capacitor C2 in the diagram, and then according to a formula: and Verr = VC1-VC2, and calculating a difference value between the positive bus capacitance voltage value and the negative bus capacitance voltage value, wherein Verr is the difference value, VC1 is the voltage value of the capacitor C1, and VC2 is the voltage value of the capacitor C2.
Further, the step of obtaining the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter includes:
step S1011, acquiring a capacitance value of a positive bus capacitor and a capacitance value of a negative bus capacitor of the grid-connected inverter;
step S1012, determining an impedance value of a positive bus capacitor according to the capacitance value of the positive bus capacitor, and determining a voltage value of the positive bus capacitor according to the impedance value of the positive bus capacitor;
step S1013, determining an impedance value of a negative bus capacitor according to the capacitance value of the negative bus capacitor, and determining a voltage value of the negative bus capacitor according to the impedance value of the negative bus capacitor.
In steps S1011 to S1013, the current harmonic control system obtains a capacitance value of a positive bus capacitor and a capacitance value of a negative bus capacitor of the grid-connected inverter, as shown in fig. 3, the capacitance value of the positive bus capacitor and the capacitance value of the negative bus capacitor are respectively a capacitance value of the capacitor C1 and a capacitance value of the capacitor C2; the current harmonic control system obtains a current value flowing through a positive bus capacitor and a negative bus capacitor, determines an impedance value of the positive bus capacitor according to the capacitance value of the positive bus capacitor, determines a voltage value of the positive bus capacitor according to the current value flowing through the positive bus capacitor and the impedance value of the positive bus capacitor, determines an impedance value of the negative bus capacitor according to the capacitance value of the negative bus capacitor, and determines a voltage value of the negative bus capacitor according to the current value flowing through the negative bus capacitor and the impedance value of the negative bus capacitor; as shown in fig. 4, the formula for calculating the impedance value of the capacitor is: 1/Cs, where C is the capacitance and s is a complex number.
And S102, inputting the difference value into a controller of the grid-connected inverter, and outputting a target fundamental frequency harmonic wave through the controller according to the difference value.
In the step, after calculating the difference value between the voltage value of the positive bus capacitor and the voltage value of the negative bus capacitor, the current harmonic control system inputs the difference value into a controller of the grid-connected inverter, and outputs a target fundamental frequency harmonic according to the difference value through the controller; as shown in fig. 4, the current harmonic control system obtains an absolute value of the difference Verr after adding and subtracting the difference Verr from 0, inputs the absolute value of the difference Verr into the controller, and the controller outputs the target fundamental frequency harmonic; wherein, the controller can select the Resonance frequency of the Resonance controller of the Proportional Resonance (PR) controller as the fundamental frequency
Further, the step of outputting, by the controller, a target fundamental frequency harmonic according to the difference includes:
and S1021, acquiring an initial fundamental frequency harmonic through the controller, and adjusting the amplitude and the phase of the initial fundamental frequency harmonic according to the difference value to obtain and output a target fundamental frequency harmonic.
In the step, the current harmonic control system obtains an initial fundamental frequency harmonic of current needing to be input into the grid-connected inverter through the controller, the initial fundamental frequency harmonic is mainly caused by unbalance of a power grid, and the amplitude and the phase of the initial fundamental frequency harmonic are adjusted through the controller according to a difference value to obtain and output a target fundamental frequency harmonic; it should be noted that the amplitude and phase of the initial fundamental frequency harmonic are adjusted so that the harmonic distortion of the finally obtained target fundamental frequency harmonic conforms to the national standard of THD (total harmonic distortion).
And S20, determining input current according to the target fundamental frequency harmonic, and inputting the input current into the grid-connected inverter to obtain output current.
In this embodiment, after the current harmonic control system outputs the target fundamental frequency harmonic through the controller, the current harmonic control system determines the input current according to the target fundamental frequency harmonic, and inputs the input current to the grid-connected inverter to obtain the output current.
Specifically, the step of determining an input current from the target fundamental frequency harmonic comprises:
step S201, determining a target voltage value according to the target fundamental frequency harmonic, and determining a pre-input current according to the target voltage value;
step S202, obtaining a preset suppression current, and determining an input current according to the preset suppression current and the preset input current.
In steps S201 to S202, the current harmonic control system calculates a target voltage value according to a target fundamental frequency harmonic in combination with a preset calculation rule, and then calculates a pre-input current according to the target voltage value; the current harmonic control system acquires a preset suppression current and determines an input current according to the preset suppression current and a preset input current; specifically, as shown in fig. 4, the current harmonic control system calculates a pre-input current according to a target voltage value through a G(s) conversion module, and obtains a pre-set suppression current I M1 Will preset the suppression current I M1 Performing preset calculation with the preset input current to obtain the input current I M 。
Further, the step of determining the pre-input current according to the target voltage value includes:
step S2011, the target voltage value is input to a conversion module of the grid-connected inverter, and a pre-input current is calculated by the conversion module according to the target voltage value and a preset transfer function.
In this step, as shown in fig. 4, the current harmonic control system inputs a target voltage value into a conversion module (G (s)) of the grid-connected inverter, and calculates a pre-input current through the conversion module according to the target voltage value and a pre-set transfer function, wherein the pre-set transfer function is G(s), which is determined according to the actual situation of the grid-connected inverter and is set in the conversion module in advance.
In the working process of the grid-connected inverter, the current harmonic control system of the embodiment judges whether the power grid unbalance degree corresponding to the power grid connected with the grid-connected inverter meets a preset condition, acquires a bus capacitor voltage value of the grid-connected inverter when the power grid unbalance degree meets the preset condition, wherein the bus capacitor voltage value comprises a positive bus capacitor voltage value and a negative bus capacitor voltage value, and calculates a difference value between the positive bus capacitor voltage value and the negative bus capacitor voltage value; the current harmonic control system inputs the difference value into a controller of the grid-connected inverter, and the controller outputs the target fundamental frequency harmonic according to the difference value; the current harmonic control system determines a target voltage value according to the target fundamental frequency harmonic and determines a pre-input current according to the target voltage value; the current harmonic control system obtains a preset suppression current, determines an input current according to the preset suppression current and a preset input current, and inputs the input current into the grid-connected inverter, so that the grid-connected inverter obtains an output current according to the input current. When the unbalance degree of the power grid is determined to meet the preset condition, the target fundamental wave frequency harmonic wave is determined according to the bus capacitor voltage value of the grid-connected inverter, and then the input current is determined according to the target fundamental wave frequency harmonic wave, so that the harmonic wave of the input current of the grid-connected inverter can be suppressed, the harmonic distortion of the output current of the grid-connected inverter is reduced, and the harmonic distortion of the output current is ensured to meet the standard.
Further, referring to fig. 5, a second embodiment of the present invention is proposed, where the second embodiment of the present invention is different from the first embodiment in that, before the step of obtaining a bus capacitor voltage value of the grid-connected inverter when it is determined that the grid imbalance degree meets the preset condition, and determining the target fundamental frequency harmonic according to the bus capacitor voltage value, the method includes:
step a, acquiring a u-phase voltage, a v-phase voltage and a w-phase voltage of a power grid, and calculating a balance degree effective value according to the u-phase voltage, the v-phase voltage and the w-phase voltage;
step b, calculating the unbalance degree of the power grid according to the effective value of the balance degree, the u-phase voltage, the v-phase voltage and the w-phase voltage;
and c, determining whether the power grid unbalance degree meets a preset condition or not according to the power grid unbalance degree and a preset unbalance threshold value.
In the embodiment, a current harmonic control system acquires a u-phase voltage, a v-phase voltage and a w-phase voltage of a power grid, and calculates an effective value of a balance degree according to the u-phase voltage, the v-phase voltage and the w-phase voltage; the current harmonic control system respectively calculates the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree according to the balance degree effective value, the u-phase voltage, the v-phase voltage and the w-phase voltage, compares the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree, determines the maximum unbalance degree, and determines the power grid unbalance degree according to the maximum unbalance degree; and the current harmonic control system determines whether the power grid unbalance degree meets a preset condition or not according to the power grid unbalance degree and a preset unbalance threshold value. It should be noted that the power grid is generally a three-phase power grid, and the u-phase voltage, the v-phase voltage, and the w-phase voltage are voltage values corresponding to three live wires of the three-phase power grid, respectively.
The current harmonic control system of the embodiment can judge whether the power grid unbalance degree meets the preset condition in advance, and then takes corresponding current harmonic control measures according to the power grid unbalance degree, so that the harmonic distortion of the output current of the grid-connected inverter is reduced, the harmonic distortion of the output current is guaranteed to meet the standard, and meanwhile, the service life of a capacitor and the efficiency of the inverter are guaranteed.
The following details the various steps:
step a, obtaining a u-phase voltage, a v-phase voltage and a w-phase voltage of a power grid, and calculating a balance degree effective value according to the u-phase voltage, the v-phase voltage and the w-phase voltage;
in the step, the current harmonic control system can directly obtain the u-phase voltage, the v-phase voltage and the w-phase voltage of the power grid according to the electrical characteristics of the power grid, and calculate the effective value of the balance degree according to the u-phase voltage, the v-phase voltage and the w-phase voltage; specifically, the formula for calculating the effective value of the balance degree according to the u-phase voltage, the v-phase voltage and the w-phase voltage is as follows: vave = (Vu + Vv + Vw)/3, where Vave is the effective value of the degree of balance, vu is the u-phase voltage, vv is the v-phase voltage, and Vw is the w-phase voltage.
Step b, calculating the unbalance degree of the power grid according to the effective value of the balance degree, the u-phase voltage, the v-phase voltage and the w-phase voltage;
specifically, step b includes:
step b1, respectively calculating the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree according to the balance degree effective value, the u-phase voltage, the v-phase voltage and the w-phase voltage;
in the step, after the current harmonic control system calculates the effective value of the balance degree, the u-phase voltage unbalance degree is calculated according to the effective value of the balance degree and the u-phase voltage, the v-phase voltage unbalance degree is calculated according to the effective value of the balance degree and the v-phase voltage, and the w-phase voltage unbalance degree is calculated according to the effective value of the balance degree and the w-phase voltage; specifically, the formula for calculating the u-phase voltage imbalance degree is as follows: h1= | (Vu-Vave) |/Vave, wherein H1 is the unbalance degree of the u-phase voltage, and Vave is the effective value of the balance degree; the formula for calculating the imbalance degree of the v-phase voltage is as follows: h2= | (Vv-Vave) |/Vave, wherein H2 is the v phase voltage unbalance degree, and Vave is the effective value of the balance degree; the formula for calculating the w-phase voltage unbalance degree is as follows: h3= | (Vw-Vave) |/Vave, where H3 is the w-phase voltage imbalance and Vave is the effective value of the balance.
And b2, comparing the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree, determining the maximum unbalance degree, and determining the power grid unbalance degree according to the maximum unbalance degree.
In the step, after the current harmonic control system calculates the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree, the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree are compared, the maximum unbalance degree is determined, and the power grid unbalance degree is determined according to the maximum unbalance degree; specifically, the formula for calculating the power grid unbalance degree is as follows: hmax = max (H1, H2, H3), where Hmax is the grid imbalance, max represents the maximum value, H1 is the u-phase voltage imbalance, H2 is the v-phase voltage imbalance, and H3 is the w-phase voltage imbalance.
And c, determining whether the power grid unbalance degree meets a preset condition or not according to the power grid unbalance degree and a preset unbalance threshold value.
In the step, after the current harmonic control system obtains the power grid unbalance degree, a preset unbalance threshold value is obtained, and the power grid unbalance degree and the preset unbalance threshold value are compared to determine whether the power grid unbalance degree meets a preset condition; specifically, the preset unbalance threshold is generally 3%, the current harmonic control system compares the power grid unbalance degree with the preset unbalance threshold, and if the power grid unbalance degree is greater than the preset unbalance threshold, whether the power grid unbalance degree meets the preset condition is determined, and a corresponding current harmonic control measure needs to be taken; and if the unbalance degree of the power grid is not larger than the preset unbalance threshold, determining whether the unbalance degree of the power grid does not accord with the preset condition or not, determining the input current according to normal logic and inputting the input current into the grid-connected inverter without taking corresponding current harmonic control measures.
The current harmonic control system of the embodiment acquires a u-phase voltage, a v-phase voltage and a w-phase voltage of a power grid, and calculates an effective value of a balance degree according to the u-phase voltage, the v-phase voltage and the w-phase voltage; the current harmonic control system respectively calculates the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree according to the balance degree effective value, the u-phase voltage, the v-phase voltage and the w-phase voltage, compares the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree, determines the maximum unbalance degree, and determines the power grid unbalance degree according to the maximum unbalance degree; and the current harmonic control system determines whether the power grid unbalance degree meets a preset condition or not according to the power grid unbalance degree and a preset unbalance threshold value. The current harmonic control system can judge whether the power grid unbalance degree meets the preset condition in advance, and then take corresponding current harmonic control measures according to the power grid unbalance degree, so that the harmonic distortion of the output current of the grid-connected inverter is reduced, the harmonic distortion of the output current is ensured to meet the standard, and meanwhile, the service life of a capacitor and the efficiency of the inverter are ensured.
Further, referring to fig. 6, a third embodiment of the present invention is proposed, which is different from the first and second embodiments in that, after the step of determining an input current according to the target fundamental frequency harmonic and inputting the input current to the grid-connected inverter to obtain an output current, the method includes:
d, determining an output voltage value according to the output current machine, and calculating the utilization rate of the output voltage;
and e, if the utilization rate of the output voltage is lower than a preset utilization rate threshold value, adjusting the voltage value of the bus capacitor according to a preset rule.
In this embodiment, since the amplitude and the phase of the fundamental frequency harmonic of the input current are changed, the amplitude and the phase of the fundamental frequency harmonic of the output current are correspondingly changed, which may result in a decrease in the utilization rate of the output voltage value, the current harmonic control system determines the output voltage value according to the output current machine and calculates the utilization rate of the output voltage, and if the utilization rate of the output voltage is lower than the preset utilization rate threshold, the bus capacitor voltage value is appropriately increased according to the preset rule, so that the utilization rate of the output voltage is greater than the preset utilization rate threshold.
The current harmonic control system of this embodiment suitably increases the bus capacitor voltage value according to the utilization ratio of output voltage for the utilization ratio of output voltage is greater than preset utilization ratio threshold value, and then improves the efficiency of inverter.
As shown in fig. 7, the present invention also provides a current harmonic control apparatus. The current harmonic control device of the present invention includes:
the determining module 101 is configured to obtain a bus capacitor voltage value of the grid-connected inverter when it is determined that the power grid imbalance meets a preset condition, and determine a target fundamental frequency harmonic according to the bus capacitor voltage value;
and the input module 102 is configured to determine an input current according to the target fundamental frequency harmonic, and input the input current to the grid-connected inverter to obtain an output current.
Further, the determining module is further configured to:
acquiring a u-phase voltage, a v-phase voltage and a w-phase voltage of a power grid, and calculating a balance degree effective value according to the u-phase voltage, the v-phase voltage and the w-phase voltage;
calculating the unbalance degree of the power grid according to the effective balance degree value, the u-phase voltage, the v-phase voltage and the w-phase voltage;
and determining whether the power grid unbalance degree meets a preset condition or not according to the power grid unbalance degree and a preset unbalance threshold value.
Further, the determining module is further configured to:
according to the balance degree effective value, the u-phase voltage, the v-phase voltage and the w-phase voltage, respectively calculating a u-phase voltage unbalance degree, a v-phase voltage unbalance degree and a w-phase voltage unbalance degree;
and comparing the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree, determining the maximum unbalance degree, and determining the power grid unbalance degree according to the maximum unbalance degree.
Further, the determining module is further configured to:
acquiring the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculating the difference value of the positive bus capacitor voltage value and the negative bus capacitor voltage value;
and inputting the difference value into a controller of the grid-connected inverter, and outputting a target fundamental frequency harmonic wave according to the difference value through the controller.
Further, the determining module is further configured to:
acquiring a capacitance value of a positive bus capacitor and a capacitance value of a negative bus capacitor of the grid-connected inverter;
determining an impedance value of a positive bus capacitor according to the capacitance value of the positive bus capacitor, and determining a voltage value of the positive bus capacitor according to the impedance value of the positive bus capacitor;
and determining the impedance value of the negative bus capacitor according to the capacitance value of the negative bus capacitor, and determining the voltage value of the negative bus capacitor according to the impedance value of the negative bus capacitor.
Further, the determining module is further configured to:
and acquiring an initial fundamental frequency harmonic through the controller, and adjusting the amplitude and the phase of the initial fundamental frequency harmonic according to the difference value to obtain and output a target fundamental frequency harmonic.
Further, the input module is further configured to:
determining a target voltage value according to the target fundamental frequency harmonic, and determining a pre-input current according to the target voltage value;
and acquiring a preset inhibiting current, and determining an input current according to the preset inhibiting current and the preset input current.
Further, the input module is further configured to:
and inputting the target voltage value into a conversion module of the grid-connected inverter, and calculating a pre-input current through the conversion module according to the target voltage value and a preset transfer function.
Further, the input module further comprises an adjustment module, the adjustment module is configured to:
determining an output voltage value according to the output current machine, and calculating the utilization rate of the output voltage;
and if the utilization rate of the output voltage is lower than a preset utilization rate threshold value, adjusting the voltage value of the bus capacitor according to a preset rule.
The invention also provides a current harmonic control system.
The current harmonic control system includes: a memory, a processor, and a current harmonic control program stored on the memory and executable on the processor, the current harmonic control program when executed by the processor implementing the steps of the current harmonic control method as described above.
The method implemented when the current harmonic control program running on the processor is executed may refer to each embodiment of the current harmonic control method of the present invention, and is not described herein again.
The invention also provides a computer readable storage medium.
The computer readable storage medium has stored thereon a current harmonic control program which, when executed by a processor, implements the steps of the current harmonic control method as described above.
The method implemented when the current harmonic control program running on the processor is executed may refer to each embodiment of the current harmonic control method of the present invention, and is not described herein again.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or system that comprises the element.
The above-mentioned serial numbers of the embodiments of the present invention are only for description, and do not represent the advantages and disadvantages of the embodiments.
Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solution of the present invention essentially or contributing to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk) as described above and includes instructions for enabling a terminal device (such as a mobile phone, a computer, a server, or a network device) to execute the method according to the embodiments of the present invention.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (12)
1. A current harmonic control method, characterized by comprising the steps of:
when the unbalanced degree of the power grid is determined to meet a preset condition, acquiring a bus capacitor voltage value of a grid-connected inverter, and determining a target fundamental frequency harmonic according to the bus capacitor voltage value;
and determining input current according to the target fundamental frequency harmonic, and inputting the input current into the grid-connected inverter to obtain output current.
2. The current harmonic control method according to claim 1, wherein before the step of obtaining a bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic according to the bus capacitor voltage value when it is determined that the grid imbalance meets the preset condition, the method comprises:
acquiring a u-phase voltage, a v-phase voltage and a w-phase voltage of a power grid, and calculating a balance degree effective value according to the u-phase voltage, the v-phase voltage and the w-phase voltage;
calculating the unbalance degree of the power grid according to the effective balance degree value, the u-phase voltage, the v-phase voltage and the w-phase voltage;
and determining whether the power grid unbalance degree meets a preset condition or not according to the power grid unbalance degree and a preset unbalance threshold value.
3. The current harmonic control method of claim 2 wherein the step of calculating the grid imbalance based on the effective value of the degree of balance, the u-phase voltage, the v-phase voltage, and the w-phase voltage comprises:
according to the balance degree effective value, the u-phase voltage, the v-phase voltage and the w-phase voltage, calculating a u-phase voltage unbalance degree, a v-phase voltage unbalance degree and a w-phase voltage unbalance degree respectively;
and comparing the u-phase voltage unbalance degree, the v-phase voltage unbalance degree and the w-phase voltage unbalance degree, determining the maximum unbalance degree, and determining the power grid unbalance degree according to the maximum unbalance degree.
4. The current harmonic control method of claim 1 wherein the bus capacitor voltage values include a positive bus capacitor voltage value and a negative bus capacitor voltage value, and wherein the step of obtaining the bus capacitor voltage value of the grid-connected inverter and determining the target fundamental frequency harmonic from the bus capacitor voltage value comprises:
acquiring the positive bus capacitor voltage value and the negative bus capacitor voltage value of the grid-connected inverter, and calculating the difference value of the positive bus capacitor voltage value and the negative bus capacitor voltage value;
and inputting the difference value into a controller of the grid-connected inverter, and outputting a target fundamental frequency harmonic wave according to the difference value through the controller.
5. The current harmonic control method of claim 4, wherein the step of obtaining the positive bus capacitor voltage value and the negative bus capacitor voltage value of a grid-tied inverter comprises:
acquiring a capacitance value of a positive bus capacitor and a capacitance value of a negative bus capacitor of the grid-connected inverter;
determining an impedance value of a positive bus capacitor according to the capacitance value of the positive bus capacitor, and determining a voltage value of the positive bus capacitor according to the impedance value of the positive bus capacitor;
and determining the impedance value of the negative bus capacitor according to the capacitance value of the negative bus capacitor, and determining the voltage value of the negative bus capacitor according to the impedance value of the negative bus capacitor.
6. The current harmonic control method of claim 4 wherein the step of outputting, by the controller, a target fundamental frequency harmonic in accordance with the difference comprises:
and acquiring an initial fundamental frequency harmonic through the controller, and adjusting the amplitude and the phase of the initial fundamental frequency harmonic according to the difference value to obtain and output a target fundamental frequency harmonic.
7. The current harmonic control method of claim 1 wherein the step of determining an input current from the target fundamental frequency harmonic comprises:
determining a target voltage value according to the target fundamental frequency harmonic, and determining a pre-input current according to the target voltage value;
and acquiring a preset suppression current, and determining an input current according to the preset suppression current and the preset input current.
8. The current harmonic control method of claim 7 wherein the step of determining a pre-input current based on the target voltage value comprises:
and inputting the target voltage value into a conversion module of the grid-connected inverter, and calculating a pre-input current through the conversion module according to the target voltage value and a preset transfer function.
9. The current harmonic control method of claim 1 wherein the step of determining an input current from the target fundamental frequency harmonic and inputting the input current to the grid-tied inverter to obtain an output current is followed by the step of:
determining an output voltage value according to the output current machine, and calculating the utilization rate of the output voltage;
and if the utilization rate of the output voltage is lower than a preset utilization rate threshold value, adjusting the voltage value of the bus capacitor according to a preset rule.
10. A current harmonic control apparatus, characterized by comprising:
the determining module is used for acquiring a bus capacitor voltage value of the grid-connected inverter when the unbalance degree of the power grid is determined to meet a preset condition, and determining a target fundamental frequency harmonic wave according to the bus capacitor voltage value;
and the input module is used for determining input current according to the target fundamental frequency harmonic and inputting the input current into the grid-connected inverter to obtain output current.
11. A current harmonic control system, comprising: memory, a processor and a current harmonic control program stored on the memory and executable on the processor, the current harmonic control program when executed by the processor implementing the steps of the current harmonic control method of any of claims 1 to 9.
12. A computer-readable storage medium, having stored thereon a current harmonic control program, which when executed by a processor, implements the steps of the current harmonic control method of any of claims 1 to 9.
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