CN114244173A - Grid voltage feedforward method for weak grid AC device, electronic equipment and medium - Google Patents

Grid voltage feedforward method for weak grid AC device, electronic equipment and medium Download PDF

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CN114244173A
CN114244173A CN202111537403.6A CN202111537403A CN114244173A CN 114244173 A CN114244173 A CN 114244173A CN 202111537403 A CN202111537403 A CN 202111537403A CN 114244173 A CN114244173 A CN 114244173A
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grid
inverter
weak
output
voltage
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宋少敏
钱红稳
周浩
姜永立
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Hefei Huawei Automation Co ltd
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Hefei Huawei Automation Co ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01Arrangements for reducing harmonics or ripples
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381Dispersed generators
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00Details of apparatus for conversion
    • H02M1/08Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40Arrangements for reducing harmonics

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  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a grid voltage feedforward method for a weak grid AC device, electronic equipment and a medium, wherein the method comprises the following steps: determining an output impedance model of the grid-connected inverter; calculating to obtain an equivalent model of the grid-connected inverter connected with the weak power grid according to an expression of output impedance in an output impedance model of the grid-connected inverter; calculating the grid-connected current of the inverter on an alpha axis according to the equivalent model of the grid-connected inverter connected with the weak power grid; determining a stable operation condition of the grid-connected inverter; a third-order generalized integral filter is added in a power grid voltage feedforward channel. The invention can not only improve the stability of the grid-connected inverter, but also reduce the influence of background harmonic waves at the voltage of a power grid on the quality of grid-connected current, and improve the quality of the output current of the inverter under the condition of weak power grid.

Description

Grid voltage feedforward method for weak grid AC device, electronic equipment and medium
Technical Field
The invention relates to the technical field of grid-connected inverter control, in particular to a grid voltage feedforward method for a weak grid AC device, electronic equipment and a computer readable storage medium.
Background
A grid-tie inverter (GTI) is a special inverter, which can convert dc power into ac power, and output ac power can be synchronized with the frequency and phase of the commercial power, so that the output ac power can be returned to the commercial power. Grid-tied inverters are commonly used in some applications where a dc voltage source (e.g., solar panels or small wind generators) is connected to the grid.
The grid-connected inverter is a power conversion device, is a bridge for connecting a distributed power supply and a public power grid, and plays a key role in the field of new energy power generation. However, with the increasing permeability of new energy power generation and the access of nonlinear loads, the power grid sometimes shows weak grid characteristics with increased grid impedance. In weak grid conditions, an increase in grid impedance will affect the inverter output current. Generally, a grid-connected inverter suppresses the influence of voltage background harmonic waves and fundamental wave components at a common grid-connected point on the output power quality of the grid-connected inverter through grid voltage feedforward control.
In the proposed grid-connected inverter control method, the grid voltage feedforward control method reduces the phase margin of the output impedance of the grid-connected inverter to a certain extent, which is not beneficial to the stable operation of the inverter.
It is therefore desirable to provide a new grid voltage feed forward method for weak grid ac machines to solve the above problems.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a grid voltage feedforward method for a weak grid AC device, electronic equipment and a medium, wherein a high-order generalized integral filter is only required to be added into a grid voltage feedforward channel, so that the robustness of a grid-connected inverter to grid impedance under the condition of a weak grid is improved.
In order to solve the technical problems, the invention adopts the following technical scheme.
A grid voltage feedforward method for a weak grid AC device is characterized by comprising the following steps:
step 1: determining an output impedance model of the grid-connected inverter;
step 2: calculating to obtain an equivalent model of the grid-connected inverter connected with the weak power grid according to an expression of output impedance in the output impedance model of the grid-connected inverter in the step 1;
and step 3: calculating the grid-connected current i of the inverter on the alpha axis according to the equivalent model of the grid-connected inverter connected with the weak power grid in the step 22_a(s);
And 4, step 4: determining a stable operation condition of the grid-connected inverter;
and 5: a third-order generalized integral filter is added in a power grid voltage feedforward channel.
Preferably, in step 1, in the output impedance model of the grid-connected inverter, the output impedance Z of the grid-connected inverter0(s) is:
Figure BDA0003413398580000021
in the above formula (1), Z0(s) represents the output impedance of the grid-connected inverter, Tm(s) is Gx1(s)、Gx2(s) and Hi2The product of (a); gx2(s) is the equivalent control link on the right side of the forward channel of the control block diagram of the alpha shaft of the inverter, FfAnd(s) is an equivalent control link containing the voltage feedforward of the power grid.
In the above formula (1), the output impedance of the grid-connected inverter is Z0And(s) is obtained according to a schematic diagram of a three-phase grid-connected inverter system under a two-phase static coordinate system in the figure 1.
Preferably, in the step 3, the grid-connected current i of the inverter on the alpha axis2_a(s) is:
Figure BDA0003413398580000022
in the above formula (2), Z0(s) watchOutput impedance of the grid-connected inverter, Zg(s) is the equivalent impedance of the grid, i0(s) is the inverter output current, Vg_a(s) is the grid voltage component on the alpha axis.
Preferably, in step 4, the stable operation condition of the grid-connected inverter is:
output impedance Z of grid-connected inverter0(s) equivalent impedance Z to the gridg(s) when the amplitude-frequency characteristic curves of the two transfer functions do not have an intersection point, the grid-connected inverter stably operates; when the amplitude-frequency characteristic curves of the inverter and the inverter have intersection points, the phase difference of the intersection points of the amplitude-frequency characteristic curves of the inverter and the inverter is required to be within +/-180 degrees, and the inverter can be ensured to operate stably.
Preferably, in the third-order generalized integral filter, three output voltage signals u1(t)、u2(t) and u3(t) the transfer function for the input voltage signal u (t) is G1(s)、G2(s) and G3(s)。
Preferably, said G1(s) is:
Figure BDA0003413398580000031
in the above formula (4), G1(s) output voltage signal u1(t), k is the gain factor, ω is the angular frequency; u shape1(s) represents a voltage signal u1(t) output of the S domain, U (S) representing a voltage signal u1(t) S-field input.
Preferably, said G2(s) is:
Figure BDA0003413398580000032
in the above formula (5), G2(s) output voltage signal u2(t), k is the gain factor, ω is the angular frequency; u shape2(s) represents a voltage signal u2(t) output of the S domain, U (S) representing a voltage signal u2(t) S-field input.
Preferably, said G3(s) is:
Figure BDA0003413398580000033
in the above formula (6), G3(s) output voltage signal u3(t), k is the gain factor, ω is the angular frequency; u shape3(s) represents a voltage signal u3(t) output of the S domain, U (S) representing a voltage signal u3(t) S-field input.
The present invention also provides an electronic device, comprising: at least one processor; and a memory communicatively coupled to the at least one processor; wherein,
the memory stores instructions executable by the at least one processor to enable the at least one processor to perform a grid voltage feed forward method for a weak grid ac according to any one of claims 1 to 8.
The invention also provides a computer readable storage medium storing a computer program which, when executed by a processor, implements the grid voltage feed-forward method for a weak grid ac according to any one of claims 1 to 8.
The invention has the beneficial effects that:
the invention discloses a grid voltage feedforward method for a weak grid AC device, electronic equipment and a medium, wherein the method comprises the following steps: determining an output impedance model of the grid-connected inverter; calculating to obtain an equivalent model of the grid-connected inverter connected with the weak power grid according to an expression of output impedance in an output impedance model of the grid-connected inverter; calculating the grid-connected current of the inverter on an alpha axis according to the equivalent model of the grid-connected inverter connected with the weak power grid; determining a stable operation condition of the grid-connected inverter; a third-order generalized integral filter is added in a power grid voltage feedforward channel.
1. The invention enables the output impedance of the grid-connected inverter to have higher amplitude in the whole frequency band, and effectively inhibits the harmonic wave of the grid-connected current.
2. According to the invention, only a high-order generalized integral filter is added in a voltage feedforward channel of the power grid, so that the robustness of the grid-connected inverter to the impedance of the power grid under the condition of weak power grid is improved, and the implementation mode is simple and efficient.
The grid voltage feedforward method, the electronic equipment and the medium for the weak grid AC device can improve the stability of the grid-connected inverter, reduce the influence of background harmonic waves at the grid voltage on the quality of grid-connected current and improve the quality of the output current of the inverter under the condition of a weak grid.
Drawings
Fig. 1 is a schematic diagram of a three-phase grid-connected inverter system in a two-phase stationary coordinate system according to the present invention.
Fig. 2 is an equivalent model of the grid-tied inverter shown connected to a weak grid.
Fig. 3 is a control block diagram of the higher order generalized integral filter of the present invention.
Fig. 4 is a block diagram of a system control after the addition of a higher order generalized integral filter.
Fig. 5 is a simplified control model of the grid-tied inverter output impedance derived from the schematic of the three-phase grid-tied inverter system of fig. 1.
FIG. 6 is the output impedance Z of the grid-connected inverter using the control method of the present invention0Bode diagram of(s).
The context and description of the various parameters in figures 1-6 are explained as follows.
Hi1As a coefficient of current feedback of the capacitor
Hi2For feedback coefficient of grid-connected current
HvSampling coefficient for network voltage
Gff(s) is a network voltage feedforward control link
Gi(s) is PR controlled current regulator
Theta denotes the phase angle of the output of the phase-locked loop
I represents a grid-connected current reference value
i0(s) is the output current of the grid-connected inverter,
Z0(s) is the output impedance of the grid-connected inverter;
i2_a(s) is the grid-connected current of the inverter on the alpha axis;
Zg(s) equivalent impedance of the weak network connected thereto
Vg_aFor the grid voltage component on the alpha axis,
omega represents the angular frequency of the output of the phase-locked loop
i*2_a(s) is a grid-connected current reference value of the inverter on an alpha axis;
Ginv(s) is an inverse bridge transfer function
ZL1(s) is the equivalent impedance of the inverter side inductor
ZL2(s) is the equivalent impedance of the network side inductor
Zc(s) is the equivalent impedance of the filter capacitor
Tm(s) is Gx1(s)、Gx2(s) and Gi2The product of (a);
Gx1(s) is the equivalent control link on the left side of the forward channel of the control block diagram of the alpha shaft of the inverter
Gx2(s) is an equivalent control link on the right side of a forward channel of an inverter alpha shaft control block diagram,
Ff(s) is an equivalent control link including voltage feedforward of the power grid
Zg(s) is the equivalent impedance of the weak grid connected,
filter represents a high-order generalized integral Filter.
Z01Representing the inverter output impedance when grid voltage feed-forward is not employed;
Z02representing the inverter output impedance including grid voltage feed-forward when controlled by PR,
LfcIs Z01、Z02Middle frequency band lower limit of Bode diagram
HfcIs Z01、Z02The upper frequency limit of the middle frequency band of the Bode diagram.
Detailed Description
The following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, will make the advantages and features of the invention easier to understand by those skilled in the art, and thus will clearly and clearly define the scope of the invention.
Referring to fig. 1-6, a grid voltage feed-forward method for a weak grid ac unit according to the present invention includes the following steps:
step 1: determining an output impedance model of the grid-connected inverter;
step 2: calculating to obtain an equivalent model of the grid-connected inverter connected with the weak power grid according to an expression of output impedance in the output impedance model of the grid-connected inverter in the step 1;
and step 3: calculating the grid-connected current i of the inverter on the alpha axis according to the equivalent model of the grid-connected inverter connected with the weak power grid in the step 22_a(s);
And 4, step 4: determining a stable operation condition of the grid-connected inverter;
and 5: a third-order generalized integral filter is added in a power grid voltage feedforward channel.
Further, in step 1, in the output impedance model of the grid-connected inverter, the output impedance Z of the grid-connected inverter0(s) is:
Figure BDA0003413398580000061
in the above formula (1), Z0(s) represents the output impedance of the grid-connected inverter, Tm(s) is Gx1(s)、Gx2(s) and Hi2The product of (a); gx2(s) is the equivalent control link on the right side of the forward channel of the control block diagram of the alpha shaft of the inverter, FfAnd(s) is an equivalent control link containing the voltage feedforward of the power grid.
In the above formula (1), the output impedance of the grid-connected inverter is Z0And(s) is obtained according to a schematic diagram of a three-phase grid-connected inverter system under a two-phase static coordinate system in the figure 1.
Further, in the step 3, the grid-connected current i of the inverter on the alpha axis2_a(s) is:
Figure BDA0003413398580000062
in the above formula (2), Z0(s) represents the output impedance of the grid-connected inverter, Zg(s) is the equivalent impedance of the grid, i0(s) is the inverter output current, Vg_a(s) is the grid voltage component on the alpha axis.
According to the output impedance Z of the grid-connected inverter0The equivalent model of the grid-connected inverter connected to the weak grid obtained by equation (1) of(s) is shown in fig. 2. According to the figure 2, the equivalent model of the grid-connected inverter accessed to the weak grid obtains the grid-connected current i of the grid-connected inverter on the alpha axis2_a(s) the above formula (2).
Grid-connected inverter in ideal grid condition (Z)g(s) ═ 0) system stability, but in the case of weak grids, the stability of the grid-tied inverter system will be governed by the right bracket term Zg(s)/Z0(s) determining.
The nyquist stability criterion shows that: output impedance Z of grid-connected inverter0(s) equivalent impedance Z to the gridg(s) when the two transfer function amplitude-frequency characteristic curves do not have an intersection point, the grid-connected inverter can stably operate; when the amplitude-frequency characteristic curves of the inverter and the inverter have intersection points, the inverter can be ensured to stably operate only when the phase difference of the intersection points of the amplitude-frequency characteristic curves of the inverter and the inverter is within +/-180 degrees;
according to the output impedance Z of the grid-connected inverter0(s) obtaining the output impedance Z of the grid-connected inverter according to the schematic diagram of the three-phase grid-connected inverter system under the two-phase static coordinate system in the figure 10A simplified control model for(s) is shown in fig. 5. According to the graph of FIG. 5, the equivalent model of the grid-connected inverter accessed to the weak grid obtains the grid-connected current i of the grid-connected inverter on the alpha axis2_a(s) is represented by the following formula (3).
Figure BDA0003413398580000071
In the formula (3), Tm(s) is a ring of the simplified control model of FIG. 5Road gain, Tm(s) is Gx1(s)、Gx2(s) and Hi2The product of (a).
Further, in step 4, the stable operation conditions of the grid-connected inverter are as follows:
output impedance Z of grid-connected inverter0(s) equivalent impedance Z to the gridg(s) when the amplitude-frequency characteristic curves of the two transfer functions do not have an intersection point, the grid-connected inverter stably operates; when the amplitude-frequency characteristic curves of the inverter and the inverter have intersection points, the phase difference of the intersection points of the amplitude-frequency characteristic curves of the inverter and the inverter is required to be within +/-180 degrees, and the inverter can be ensured to operate stably.
Furthermore, in the third-order generalized integral filter, three output voltage signals u1(t)、u2(t) and u3(t) the transfer function for the input voltage signal u (t) is G1(s)、G2(s) and G3(s)。
Further, said G1(s) is:
Figure BDA0003413398580000072
in the above formula (4), G1(s) output voltage signal u1(t), k is the gain factor, ω is the angular frequency; u shape1(s) represents a voltage signal u1(t) output of the S domain, U (S) representing a voltage signal u1(t) S-field input.
Further, said G2(s) is:
Figure BDA0003413398580000073
in the above formula (5), G2(s) output voltage signal u2(t), k is the gain factor, ω is the angular frequency; u shape2(s) represents a voltage signal u2(t) output of the S domain, U (S) representing a voltage signal u2(t) S-field input.
Further, said G3(s) is:
Figure BDA0003413398580000074
in the above formula (6), G3(s) output voltage signal u3(t), k is the gain factor, ω is the angular frequency; u shape3(s) represents a voltage signal u3(t) output of the S domain, U (S) representing a voltage signal u3(t) S-field input.
In summary, a third-order generalized integral filter is added in a voltage feedforward channel of a power grid, the third-order generalized integral filter is a two-input three-output system, the input of the system is angular frequency omega and a voltage signal u (t), and the output is u1(t)、u2(t) and u3(t) of (d). Transfer function G of three output voltage signals to input voltage signal1(s)、G2(s) and G3(s) are as defined in the above formulae (4) to (6), respectively.
The present invention also provides an electronic device, comprising: at least one processor; and a memory communicatively coupled to the at least one processor; wherein,
the memory stores instructions executable by the at least one processor to enable the at least one processor to perform a grid voltage feed forward method for a weak grid ac according to any one of claims 1 to 8.
The invention also provides a computer readable storage medium storing a computer program which, when executed by a processor, implements the grid voltage feed-forward method for a weak grid ac according to any one of claims 1 to 8.
The invention discloses a grid voltage feedforward method for a weak grid AC device, electronic equipment and a medium, and aims to solve the problem that the stability of a grid-connected inverter is influenced by the fact that the output impedance phase margin of an inverter is reduced under the condition of a weak grid in the prior art. The invention can not only improve the stability of the grid-connected inverter, but also reduce the influence of background harmonic waves at the voltage of a power grid on the quality of grid-connected current, and improve the quality of the output current of the inverter under the condition of weak power grid.
According to the characteristics of a grid-connected inverter and grid impedance under the condition of a weak grid, a high-order generalized integral filter is added into a grid voltage feedforward channel, and a system control block diagram is shown in fig. 4.
Fig. 6 is a bode plot of the output impedance of a grid-connected inverter using the control strategy of the present invention. In the figure, Z0(s) represents the output impedance, Z, of the present invention01Indicating inverter output impedance, Z, without grid voltage feed-forward02Representing inverter output impedance, Z, with grid voltage feed-forward when controlled with PRgRepresenting the grid equivalent impedance. As can be seen from fig. 6, before the present invention is adopted, the phase margin of the inverter output impedance is low in a certain frequency band, so that the phase difference between the inverter output impedance and the equivalent impedance of the power grid exceeds ± 180 degrees, and the inverter cannot stably operate; after the method is adopted, the output impedance of the inverter has higher amplitude in the whole frequency band of the Bode diagram, and the phase margin is improved, so that the grid-connected inverter can still stably operate even under the condition of weak power grid. The control method for adding the high-order generalized integral filter into the voltage feedforward channel of the power grid can improve the stability of the grid-connected inverter under the condition of weak power grid and effectively improve the quality of grid-connected current.
The invention provides a power grid voltage feedforward control method using a high-order generalized integral filter aiming at the problem of low output current quality of a power grid voltage feedforward inverter under the condition of a weak power grid.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (10)

1. A grid voltage feedforward method for a weak grid ac machine is characterized by comprising the following steps:
step 1: determining an output impedance model of the grid-connected inverter;
step 2: calculating to obtain an equivalent model of the grid-connected inverter connected with the weak power grid according to an expression of output impedance in the output impedance model of the grid-connected inverter in the step 1;
and step 3: calculating the grid-connected current i of the inverter on the alpha axis according to the equivalent model of the grid-connected inverter connected with the weak power grid in the step 22_a(s);
And 4, step 4: determining a stable operation condition of the grid-connected inverter;
and 5: a third-order generalized integral filter is added in a power grid voltage feedforward channel.
2. The grid voltage feedforward method for the weak grid ac machine according to claim 1, wherein in step 1, in the output impedance model of the grid-connected inverter, the output impedance Z of the grid-connected inverter0(s) is:
Figure FDA0003413398570000011
in the above formula (1), Z0(s) represents the output impedance of the grid-connected inverter, Tm(s) is Gx1(s)、Gx2(s) and Hi2The product of (a); gx2(s) is the equivalent control link on the right side of the forward channel of the control block diagram of the alpha shaft of the inverter, FfAnd(s) is an equivalent control link containing the voltage feedforward of the power grid.
3. Grid voltage feed-forward method for weak grid ac machines according to claim 1, characterized in that in step 3, the grid-connected current i of the inverter on the α -axis2_a(s) is:
Figure FDA0003413398570000012
in the above formula (2), Z0(s) represents the output impedance of the grid-connected inverter, Zg(s) is the equivalent impedance of the grid, i0(s) is the inverter output current, Vg_a(s) is the grid voltage component on the alpha axis.
4. The grid voltage feed-forward method for the weak grid ac machine according to claim 1, wherein in the step 4, the stable operation condition of the grid-connected inverter is:
output impedance Z of grid-connected inverter0(s) equivalent impedance Z to the gridg(s) when the amplitude-frequency characteristic curves of the two transfer functions do not have an intersection point, the grid-connected inverter stably operates; when the amplitude-frequency characteristic curves of the inverter and the inverter have intersection points, the phase difference of the intersection points of the amplitude-frequency characteristic curves of the inverter and the inverter is required to be within +/-180 degrees, and the inverter can be ensured to operate stably.
5. Grid voltage feed-forward method for weak grid ac machines according to claim 1, characterized in that in said third order generalized integral filter, three output voltage signals u1(t)、u2(t) and u3(t) transfer for input voltage signal u (t)The functions are respectively G1(s)、G2(s) and G3(s)。
6. Grid voltage feed-forward method for weak grid ac machines according to claim 5, characterized in that said G is1(s) is:
Figure FDA0003413398570000021
in the above formula (4), G1(s) output voltage signal u1(t), k is the gain factor, ω is the angular frequency; u shape1(s) represents a voltage signal u1(t) output of the S domain, U (S) representing a voltage signal u1(t) S-field input.
7. Grid voltage feed-forward method for weak grid ac machines according to claim 5, characterized in that said G is2(s) is:
Figure FDA0003413398570000022
in the above formula (5), G2(s) output voltage signal u2(t), k is the gain factor, ω is the angular frequency; u shape2(s) represents a voltage signal u2(t) output of the S domain, U (S) representing a voltage signal u2(t) S-field input.
8. Grid voltage feed-forward method for weak grid ac machines according to claim 5, characterized in that said G is3(s) is:
Figure FDA0003413398570000023
in the above formula (6), G3(s) output voltage signal u3(t), k is the gain factor, ω is the angular frequency; u shape3(s) represents a voltage signal u3(t) output of the S domain, U (S) representing a voltage signal u3(t) S-field input.
9. An electronic device, comprising:
at least one processor; and a memory communicatively coupled to the at least one processor; wherein,
the memory stores instructions executable by the at least one processor to enable the at least one processor to perform a grid voltage feed forward method for a weak grid ac according to any one of claims 1 to 8.
10. A computer-readable storage medium, storing a computer program, wherein the computer program, when executed by a processor, implements the grid voltage feed-forward method for a weak grid ac according to any one of claims 1 to 8.
CN202111537403.6A 2021-12-15 2021-12-15 Grid voltage feedforward method for weak grid AC device, electronic equipment and medium Pending CN114244173A (en)

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