CN109980627B - Oscillation suppression method and device for direct current power distribution network - Google Patents
Oscillation suppression method and device for direct current power distribution network Download PDFInfo
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- CN109980627B CN109980627B CN201910255353.9A CN201910255353A CN109980627B CN 109980627 B CN109980627 B CN 109980627B CN 201910255353 A CN201910255353 A CN 201910255353A CN 109980627 B CN109980627 B CN 109980627B
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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
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The invention relates to an oscillation suppression method and device for a direct current power distribution network, wherein the method comprises the following steps: acquiring operation parameters of each converter in the direct-current power distribution network, wherein the operation parameters comprise output voltage, output current, impedance characteristics and harmonic characteristics; acquiring a converter set which is easy to generate resonance in the direct-current power distribution network according to the operation parameters; and selecting a corresponding parameter adjusting mode according to the number of the converters in the converter set, and adjusting the parameter of each converter in the converter set according to the selected parameter adjusting mode to suppress the oscillation of the direct current distribution network, so that the dynamic suppression of the system oscillation can be realized, and the power consumption and the cost of the system cannot be increased.
Description
Technical Field
The invention relates to the technical field of direct-current power distribution networks, in particular to an oscillation suppression method and device of a direct-current power distribution network.
Background
In a direct-current distribution network, most of equipment is electrically connected with a direct-current bus through a DC/DC converter or an AC/DC converter, so that the direct-current bus not only has a direct-current component, but also inevitably has a certain harmonic component due to the influence of the switching characteristics, the load characteristics and the like of power electronic devices, and thus the parasitic inductance and the parasitic capacitance of the direct-current bus have the possibility of resonance under certain conditions. Meanwhile, a plurality of DC/DC converters or AC/DC converters often exist in the DC distribution network, and different converters are affected by factors such as power levels, topology structures, and control parameters, so that impedance characteristics and oscillation injected to the DC bus are different, and when the oscillation frequency of the converter is consistent with the natural oscillation frequency of the DC bus, the DC bus oscillates, so that the DC distribution network fails, and therefore, the oscillation of the DC bus needs to be suppressed.
In the related art, the oscillation of the dc distribution grid is mainly suppressed by the following means:
1) the method is based on a method of adding passive damping, for example, connecting resistors in series or in parallel on a filter element of a converter, and keeping a control strategy of the converter unchanged to achieve the purpose of suppressing system oscillation, but the method increases the power loss, cost and volume of the system due to the increase of the actual resistor, and is not practical due to the fact that the circuit connection is complicated and a greater risk is easy to occur.
2) The active damping method, for example, adds a control loop to generate an equivalent damping effect in a controlled system, thereby achieving the purpose of suppressing system oscillation, but since the resonant frequency changes with factors such as grid impedance, element loss, and environmental changes, when the traditional active damping method is used for suppressing oscillation, the impedance characteristic of the active damping method cannot be dynamically adjusted according to the resonant frequency, and thus it is difficult to obtain an ideal suppression effect.
3) For example, an active power filter is additionally arranged in a system, and multiple times of higher harmonics are filtered by the active power filter, so that the purpose of suppressing the system oscillation is achieved.
Although the method can solve the problem of system oscillation to a certain extent, the problems of incapability of dynamically inhibiting oscillation, high system power consumption and high cost still exist.
Disclosure of Invention
In view of the above, it is necessary to provide a method and an apparatus for suppressing oscillation in a dc power distribution network, which solve the problems in the related art that oscillation cannot be dynamically suppressed when the dc power distribution network is subjected to oscillation suppression, and that the system has large power consumption and high cost.
An oscillation suppression method for a direct current distribution network comprises the following steps:
acquiring operation parameters of each converter in the direct-current power distribution network, wherein the operation parameters comprise output voltage, output current, impedance characteristics and harmonic characteristics;
acquiring a converter set which is easy to generate resonance in the direct-current power distribution network according to the operation parameters;
and selecting a corresponding parameter adjusting mode according to the number of the converters in the converter set, and adjusting the parameter of each converter in the converter set according to the selected parameter adjusting mode so as to suppress the oscillation of the direct current distribution network.
In one embodiment, acquiring a set of converters that are susceptible to resonance in a dc power distribution network according to an operating parameter includes:
acquiring the resonant frequency of the direct-current power distribution network according to the operation parameters;
acquiring participation factors of each converter in the direct-current power distribution network corresponding to the resonant frequency;
and determining a set of converters which are easy to generate resonance according to the magnitude relation of the participation factors.
In one embodiment, the obtaining the resonant frequency of the dc power distribution network according to the operating parameters includes:
establishing a node admittance matrix of the direct current power distribution network under different preset frequencies according to the operation parameters to obtain a plurality of node admittance matrixes;
obtaining modal impedance of each node admittance matrix to obtain a plurality of modal impedances;
and acquiring the resonant frequency of the direct-current power distribution network according to the magnitude relation of the modal impedances.
In one embodiment, obtaining the participation factor of each converter in the dc power distribution network corresponding to the resonant frequency includes:
acquiring a node admittance matrix of a direct current distribution network corresponding to the resonant frequency, recording the node admittance matrix as a first node admittance matrix, and acquiring a node voltage matrix and an injection current matrix of the corresponding direct current distribution network;
obtaining a modal voltage vector and a modal current vector according to the first node admittance matrix, the node voltage matrix and the injection current matrix;
and acquiring participation factors of each converter according to the modal voltage vector and the modal current vector.
In one embodiment, determining a set of transducers susceptible to resonance according to magnitude relationships of the participation factors includes:
acquiring the maximum value of the participation factor;
judging whether the absolute value of the difference value between the residual participation factor and the maximum value is smaller than a preset threshold value or not;
if yes, the converter corresponding to the participation factor is included in the converter set.
In one embodiment, selecting a corresponding parameter adjustment mode according to the number of converters in the converter set includes:
if the number is one, the parameter adjusting mode is an active damping parameter adjusting mode;
if the number is two or more, the parameter adjusting mode is an adjusting mode combining the active damping parameters and the virtual power grid parameters.
In one embodiment, the active damping parameter adjustment is expressed by the following formula:
Z＝1-RaIo，
wherein Z is an active damping parameter, RaTo adjust the coefficients, IoIs the output current of the converter to be regulated.
In one embodiment, the combined adjustment mode of the active damping parameter and the virtual grid parameter includes:
and adjusting the active damping parameters of each converter to be adjusted, and injecting virtual power grid parameters into each converter to be adjusted so as to enable the resonant frequency of all the converters to be adjusted to be the same fixed resonant frequency and suppress the same fixed resonant frequency.
An oscillation suppression device for a direct current distribution network, comprising:
the parameter acquisition module is used for acquiring operation parameters of each converter in the direct-current power distribution network, wherein the operation parameters comprise output voltage, output current, impedance characteristics and harmonic characteristics;
the resonance generation acquisition module is used for acquiring a converter set which is easy to generate resonance in the direct-current power distribution network according to the operation parameters;
and the oscillation suppression module is used for selecting a corresponding parameter adjustment mode according to the number of the converters in the converter set, and adjusting the parameter of each converter in the converter set according to the selected parameter adjustment mode so as to suppress oscillation of the direct current distribution network.
In one embodiment, the oscillation suppression module selects the corresponding parameter adjustment mode according to the number of the converters in the converter set, wherein,
if the number is one, the parameter adjusting mode is an active damping parameter adjusting mode;
if the number is two or more, the parameter adjusting mode is an adjusting mode combining the active damping parameters and the virtual power grid parameters.
According to the oscillation suppression method and device for the direct current distribution network, the operation parameters of each converter in the direct current distribution network are obtained, wherein the operation parameters comprise output voltage, output current, impedance characteristics and harmonic characteristics, the converter set which is easy to generate resonance in the direct current distribution network is obtained according to the operation parameters, the corresponding parameter adjustment mode is selected according to the number of the converters in the converter set, and the parameter of each converter in the converter set is adjusted according to the selected parameter adjustment mode to suppress oscillation of the direct current distribution network, so that dynamic suppression of system oscillation can be achieved, and system power consumption and cost cannot be increased.
Drawings
FIG. 1 is a flow diagram of a method for oscillation suppression in a DC power distribution network in accordance with one embodiment;
FIG. 2 is a diagram of a topology of a DC distribution network in one embodiment;
FIG. 3 is a flow chart of obtaining a set of converters that are susceptible to resonance in a DC power distribution network in one embodiment;
FIG. 4 is a diagram illustrating the effect of the grid equivalent impedances of 1mH, 2mH, and 3mH on DC distribution grid resonance in one embodiment;
FIG. 5 is a diagram illustrating the effect of adaptive damping and conventional damping on the output voltage in one embodiment;
fig. 6 is a flowchart of an oscillation suppression method for a dc distribution network in a specific example;
FIG. 7 is a block diagram illustrating an apparatus for suppressing oscillations in a DC power distribution network according to one embodiment;
fig. 8 is a system diagram of oscillation suppression for a dc distribution network in an exemplary embodiment.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather should be construed as broadly as the present invention is capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
Fig. 1 is a flowchart of an oscillation suppression method for a dc power distribution network in an embodiment, and as shown in fig. 1, the oscillation suppression method for the dc power distribution network includes the following steps:
Specifically, referring to fig. 2, a DC distribution network usually includes a large number of distributed power sources (e.g., photovoltaic power generation, wind power generation), energy storage devices (e.g., energy storage system), and AC/DC loads (e.g., electric vehicle, AC load, and DC load), and these devices are connected to a DC bus through a DC/DC converter or an AC/DC converter, and during operation, the DC system fluctuates due to power fluctuation of the distributed power sources, switching of large-capacity loads, and a fault on the AC side, and harmonics generated by these fluctuations adversely affect the DC distribution network, so that it is necessary to suppress oscillation of the DC distribution network.
When the oscillation of the dc distribution network is suppressed, the operating parameters of the dc distribution network may be obtained through each converter in the dc distribution network, for example, the output voltage and the output current of the dc distribution network are detected, the impedance characteristic and the harmonic characteristic of the dc distribution network are analyzed, and then the output voltage, the output current, the impedance characteristic, the harmonic characteristic, and the like of the dc distribution network are uploaded to the upper monitoring center.
And step 104, acquiring a converter set which is easy to generate resonance in the direct current distribution network according to the operation parameters.
Specifically, after the upper monitoring center receives operation parameters of each converter in the direct current distribution network, such as output voltage, output current, impedance characteristics and harmonic characteristics, all converters which are easy to generate resonance in the direct current distribution network are determined according to the operation parameters and serve as a converter set.
In one embodiment, referring to fig. 3, obtaining a set of converters that are susceptible to resonance in a dc power distribution network according to an operating parameter includes:
and 302, acquiring the resonant frequency of the direct current distribution network according to the operation parameters.
In one embodiment, obtaining the resonant frequency of the dc distribution network based on the operating parameters comprises: establishing a node admittance matrix of the direct current power distribution network under different preset frequencies according to the operation parameters to obtain a plurality of node admittance matrixes; obtaining modal impedance of each node admittance matrix to obtain a plurality of modal impedances; and acquiring the resonant frequency of the direct-current power distribution network according to the magnitude relation of the modal impedances. Wherein, different preset frequencies can be determined according to the frequency of the resonance of the direct current distribution network.
Specifically, after the upper monitoring center receives the operating parameters of each converter in the dc power distribution network, such as output voltage, output current, impedance characteristics, and harmonic characteristics, a node admittance matrix Y1 of the converter network in the dc power distribution network at a preset frequency f1 may be established, and eigenvalue decomposition may be performed on the node admittance matrix Y1 to obtain an eigenvalue λ 1, and an absolute value or a modulus |1/λ 1| of a reciprocal 1/λ 1 of the eigenvalue λ 1 may be recorded, and defined as modal impedance. Then, a node admittance matrix Y2 of the transformer network in the direct current distribution network under the preset frequency f2 is established, eigenvalue decomposition is carried out on the node admittance matrix Y2 to obtain an eigenvalue lambda 2, and the absolute value or the modulus | 1/lambda 2| of the reciprocal 1/lambda 2 of the eigenvalue lambda 2 is recorded and defined as modal impedance. Then, the next preset frequency is switched and the above steps are repeated, the frequency can be changed from small to large until all the frequencies where resonance is possible are traversed, and if n frequencies are provided, the distribution of the absolute value or the mode value (i.e. modal impedance) of the reciprocal of the characteristic value corresponding to the n modes can be finally obtained.
Then, the absolute value of the reciprocal of the characteristic value corresponding to the n modes or the maximum value of the mode value (i.e., the modal impedance) is obtained to obtain the maximum modal impedance. After the maximum modal impedance is obtained, the condition corresponding to the maximum modal impedance can be used as the key parallel resonance of the system, the corresponding characteristic value is used as the key mode, and the frequency corresponding to the peak value is the resonance frequency of the parallel resonance, namely the resonance frequency of the direct-current power distribution network.
And 304, acquiring participation factors of all converters in the direct current distribution network corresponding to the resonant frequency.
In one embodiment, obtaining the participation factor of each converter in the dc distribution network corresponding to the resonant frequency includes: acquiring a node admittance matrix of a direct current distribution network corresponding to the resonant frequency, recording the node admittance matrix as a first node admittance matrix, and acquiring a node voltage matrix and an injection current matrix of the corresponding direct current distribution network; obtaining a modal voltage vector and a modal current vector according to the first node admittance matrix, the node voltage matrix and the injection current matrix; and acquiring participation factors of each converter according to the modal voltage vector and the modal current vector.
Specifically, after the resonant frequency of the dc power distribution network is obtained, the node admittance matrix Y of the dc power distribution network corresponding to the resonant frequency may be obtained first, and then the left and right characteristic vector matrices may be obtained, and the participation factor of each converter to the current mode may be obtained from the left and right characteristic vector matrices.
Specifically, assuming that the modal impedance corresponding to the preset frequency f2 is the maximum modal impedance, the preset frequency f2 is the resonant frequency of the dc power distribution network, at this time, the upper monitoring center first establishes a node admittance matrix Y of the transformer network in the dc power distribution network at the preset frequency f2, and obtains a node voltage matrix V and an injection current matrix I of the dc power distribution network at the preset frequency f2, and the node admittance matrix Y, the node voltage matrix V and the injection current matrix I have the following relationships:
V＝Y-1*I (1)
meanwhile, the following formula (2) can be obtained according to the matrix decomposition node admittance matrix Y:
Y＝LΛT (2)
wherein Λ is a eigenvalue matrix of the node admittance matrix Y, the matrix L is a left eigenvector matrix, and the matrix T is a right eigenvector matrix. Then, substituting the above equation (2) into equation (1) can obtain the following equation:
V＝LΛ-1TI or TV ═ Λ-1TI (3)
Wherein, defining U ═ TV as the modal voltage vector and J ═ TI as the modal current vector, and then substituting the obtained output voltage matrix and output current matrix of each converter into the above formula (3), the modal voltage vector and modal current vector can be obtained.
Then, a relationship between the modal voltage vector and the modal current vector is established, and the following formula can be further obtained:
U＝Λ-1j or
As can be seen from the above equation (4), the participation factors of the converters of the current mode (resonant frequency f2) are:
…, obtaining the participation factor of each converter in the DC distribution network corresponding to the resonance frequency.
And step 306, determining a set of converters which are easy to generate resonance according to the magnitude relation of the participation factors.
In one embodiment, determining a set of transducers susceptible to resonance based on a magnitude relationship of the participation factors includes: acquiring the maximum value of the participation factor; judging whether the absolute value of the difference value between the residual participation factor and the maximum value is smaller than a preset threshold value or not; if yes, the converter corresponding to the participation factor is included in the converter set. The preset threshold value can be calibrated according to actual conditions.
Specifically, after the participation factors of each converter in the dc distribution network corresponding to the resonant frequency are obtained, which converters are more likely to cause oscillation can be determined according to the magnitude relationship of the participation factors, so as to determine a converter set that is likely to generate resonance. For example, the maximum value of the participation factor may be obtained from all the participation factors, and then the remaining participation factors are determined one by one to determine whether the absolute value of the difference between each remaining participation factor and the maximum value is smaller than a preset threshold, that is, whether each remaining participation factor is close to the maximum value is determined, if yes, it is considered that the converter corresponding to the participation factor is easy to generate resonance, and at this time, the converter is incorporated into the converter set; otherwise, discarding the converter corresponding to the participation factor.
And 106, selecting a corresponding parameter adjusting mode according to the number of the converters in the converter set, and adjusting the parameter of each converter in the converter set according to the selected parameter adjusting mode so as to suppress oscillation of the direct current distribution network.
In one embodiment, selecting a corresponding parameter adjustment mode according to the number of converters in the converter set includes: if the number is one, the parameter adjusting mode is an active damping parameter adjusting mode; if the number is two or more, the parameter adjusting mode is an adjusting mode combining the active damping parameters and the virtual power grid parameters.
Specifically, when only one of all the participation factors is large, it is shown that only the converter corresponding to the participation factor is easy to induce oscillation, and at this time, the parameter of the converter is adjusted by adopting an active damping parameter adjustment mode, so that the suppression of the oscillation of the dc distribution network can be realized. For example, the above formula (4) is taken as an example. Suppose, that factor P is involved1At the maximum of all the participation factors and much greater than the remaining ones, the converter susceptible to resonance has only one, i.e. the participation factor P1And at the moment, the upper monitoring center can select an active damping parameter adjustment mode to adjust the parameters of the converter, so that the oscillation of the direct current distribution network is suppressed.
In one embodiment, the active damping parameter adjustment is expressed by the following equation:
Z＝1-RaIo(5)
wherein Z is an active damping parameter, RaTo adjust the coefficients, IoIs the output current of the converter to be regulated.
Specifically, when the active damping parameter of the converter is adjusted, although it is beneficial to suppress the resonance that may occur in the converter, the output voltage of the converter may decrease, so in order to suppress the resonance that may occur in the converter and reduce the influence on the output voltage of the converter, an adaptive active damping adjustment method may be adopted, that is, a single active damping parameter is set to be a function related to the output current, as shown in the above formula (5), so that the active damping parameter is adaptively adjusted along with the change of the current, and the voltage drop of the output voltage is further reduced, as shown in fig. 5 in particular. Therefore, when only one converter in the direct current distribution network easily causes oscillation, effective suppression of the direct current distribution network oscillation can be achieved through adaptive adjustment of the active damping parameter.
Further, when a plurality of participation factors are large and close to each other in all the participation factors, erroneous judgment is easily caused on the resonance influence of the converters corresponding to the participation factors on the system, so that in order to further accurately suppress the resonance of the direct current distribution network, a virtual power grid parameter is introduced at the moment, and the oscillation of the direct current distribution network is suppressed through the virtual power grid parameter. Specifically, when a plurality of converters are connected to a dc distribution network, since the power levels and filter parameters of the converters themselves are fixed, the resonant frequencies of the converters themselves remain substantially unchanged, and the grid-connected resonant frequency of the converters decreases as the equivalent impedance of the power grid increases, as shown in fig. 4, so that by injecting different virtual grid parameters such as virtual grid impedance into the converters, the resonant frequency of the converter having a large participation factor and being close to the large participation factor can be shifted to a certain fixed resonant frequency, and then the fixed resonant frequency is suppressed (e.g., filtered), so that the dc distribution network oscillation can be suppressed.
In practical application, in order to achieve a better suppression effect, the oscillation of the direct current distribution network can be suppressed by adopting an adjustment mode of combining active damping parameters and virtual power network parameters. In one embodiment, the combined adjustment mode of the active damping parameter and the virtual grid parameter includes: and adjusting the active damping parameters of each converter to be adjusted, and injecting virtual power grid parameters into each converter to be adjusted so as to enable the resonant frequency of all the converters to be adjusted to be the same fixed resonant frequency and suppress the same fixed resonant frequency.
Specifically, the above example is still exemplified. If participating in the factor P2Is close to the maximum value P1And much larger than the remaining participation factor, i.e. P2≈P1＞＞P3…, it is not possible to determine which transducer is more susceptible to excitation and resonance, so the upper monitoring center may select an active resistorAdjustment mode pair participation factor P combining damping parameter and virtual power grid parameter1And P2The parameters of the corresponding converter are adjusted. For example, P can be first and separately paired1And P2The active damping parameters of the corresponding converter are adjusted in a single active damping parameter adjusting method or the self-adaptive active damping adjusting method, and then the adjustment is respectively carried out to P1And P2The corresponding converter injects a virtual grid parameter, such as virtual grid impedance, to P1And P2The output impedance of the corresponding converter and the equivalent impedance of the power grid are dynamically adjusted, so that a direct-current distribution network resonant network is damaged, the dispersed multipoint resonant frequencies are unified into a certain fixed resonant frequency, and then the oscillation which possibly occurs to the system can be suppressed by suppressing (such as filtering) the fixed resonant frequency. Therefore, when two or more converters in the direct current distribution network easily cause oscillation, effective suppression of the direct current distribution network oscillation can be achieved through adjustment of the active damping parameters and the virtual power network parameters.
Fig. 6 is a flowchart of an oscillation suppression method for a dc power distribution network in a specific example, and as shown in fig. 6, the oscillation suppression method for the dc power distribution network may include the following steps:
step 602, the upper monitoring center obtains output voltage, output current, impedance characteristics and harmonic characteristics of each converter in the dc power distribution network.
Step 604, establishing a node admittance matrix of the direct current distribution network under the preset frequency.
And 606, calculating the eigenvalue of the node admittance matrix, and recording the absolute value or the modulus of the reciprocal of the eigenvalue.
In step 608, the frequency is changed from small to large until all frequencies which may resonate are traversed, and the distribution of the absolute value or the modulus of the reciprocal of the eigenvalue corresponding to the n modes is obtained.
And step 610, judging and obtaining the resonant frequency of the direct current distribution network according to the absolute value of the reciprocal of the characteristic value or the magnitude of the mode value corresponding to the n modes.
And step 612, solving a node admittance matrix of the direct current power distribution network at the moment according to the resonance frequency, further obtaining a left eigenvector matrix and a right eigenvector matrix, solving the participation factor of each converter to the current mode according to the left eigenvector matrix and the right eigenvector matrix, and obtaining the converter with a larger participation factor.
And 614, the upper monitoring center sends adjusting parameters such as active damping parameters or active damping parameters and virtual power grid parameters to the converter with larger participation factors to change the impedance characteristics of the converter, so that the oscillation of the system is inhibited.
In this embodiment, each converter in the dc power distribution network uploads its own voltage and current information, impedance characteristics, and harmonic characteristic information to the upper monitoring center, and the upper monitoring center obtains the harmonic characteristic distribution of the entire dc power distribution network and the resonant frequency at which resonance may occur through analysis, and further calculates the active damping parameters and virtual grid parameters that each converter needs to adjust, and sends the active damping parameters and virtual grid parameters to each converter in the system, thereby dynamically adjusting the impedance characteristics of each converter in the system, suppressing the resonance that may occur in the system, and ensuring the security of the entire system.
In summary, the oscillation suppression method for the dc distribution network dynamically adjusts the impedance characteristics of each converter in the system based on the harmonic measurement of each converter in the dc distribution network, so that the harmonic frequency of each converter deviates from the resonant frequency point, thereby suppressing the oscillation that may occur in the system, improving the overall safety of the dc distribution network, and not increasing the system power consumption and cost.
Fig. 7 is a block diagram illustrating an oscillation suppression apparatus for a dc power distribution network according to an embodiment, where as shown in fig. 7, the oscillation suppression apparatus for the dc power distribution network includes: a parameter acquisition module 10, a resonance generation acquisition module 20 and an oscillation suppression module 30.
The parameter obtaining module 10 is configured to obtain operation parameters of each converter in the dc power distribution network, where the operation parameters include output voltage, output current, impedance characteristics, and harmonic characteristics; the resonance generation acquisition module 20 is configured to acquire a converter set that is easy to generate resonance in the dc power distribution network according to the operation parameters; the oscillation suppression module 30 is configured to select a corresponding parameter adjustment manner according to the number of converters in the converter set, and adjust a parameter of each converter in the converter set according to the selected parameter adjustment manner, so as to perform oscillation suppression on the dc distribution network. In practical applications, as shown in fig. 8, one parameter obtaining module 10 may be provided for each converter, and the resonance generation obtaining module 20 and the oscillation suppression module 30 may be integrally provided in the upper monitoring center, which is not limited herein.
In one embodiment, when the oscillation suppression module 30 selects the corresponding parameter adjustment mode according to the number of the converters in the converter set, if the number is one, the parameter adjustment mode is the active damping parameter adjustment mode; if the number is two or more, the parameter adjusting mode is an adjusting mode combining the active damping parameters and the virtual power grid parameters.
It should be noted that, for the description of the oscillation suppression device for the dc power distribution network, reference may be made to the description of the oscillation suppression method for the dc power distribution network, and details are not repeated here.
According to the oscillation suppression device for the direct current distribution network, the operation parameters of each converter in the direct current distribution network are obtained, the converter set which is easy to generate resonance in the direct current distribution network is obtained according to the operation parameters, the corresponding parameter adjustment mode is selected according to the number of the converters in the converter set, and the parameter of each converter in the converter set is adjusted according to the selected parameter adjustment mode so as to suppress oscillation of the direct current distribution network, so that dynamic suppression of system oscillation can be achieved, and system power consumption and cost cannot be increased.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (8)
1. An oscillation suppression method for a direct current distribution network is characterized by comprising the following steps:
obtaining operation parameters of each converter in a direct current power distribution network, wherein the operation parameters comprise output voltage, output current, impedance characteristics and harmonic characteristics;
obtaining a converter set which is easy to generate resonance in the direct current distribution network according to the operation parameters, wherein the converter set comprises: acquiring the resonant frequency of the direct current distribution network according to the operation parameters; acquiring participation factors of each converter in the direct-current power distribution network corresponding to the resonant frequency; determining a converter set which is easy to generate resonance according to the magnitude relation of the participation factors; determining a converter set which is easy to generate resonance according to the magnitude relation of the participation factors, wherein the converter set comprises: acquiring the maximum value of the participation factor; judging whether the absolute value of the difference value between the residual participation factor and the maximum value is smaller than a preset threshold value or not; if yes, the converter corresponding to the participation factor is included in the converter set;
selecting a corresponding parameter adjusting mode according to the number of the converters in the converter set, if the number is one, the parameter adjusting mode is an active damping parameter adjusting mode, if the number is two or more, the parameter adjusting mode is an adjusting mode combining active damping parameters and virtual power grid parameters, and adjusting the parameters of each converter in the converter set according to the selected parameter adjusting mode so as to suppress oscillation of the direct current power distribution network.
2. The method of claim 1, wherein obtaining operating parameters for each converter in the dc power distribution network comprises:
detecting the output voltage and the output current of the respective converters, and analyzing the impedance characteristics and the harmonic characteristics of the respective converters;
uploading the output voltage, the output current, the impedance characteristic, and the harmonic characteristic to an upper monitoring center.
3. The method of claim 2, wherein obtaining a set of converters in the dc distribution network susceptible to resonance according to the operating parameters comprises:
after the upper monitoring center receives the output voltage, the output current, the impedance characteristic and the harmonic characteristic, acquiring a converter set which is easy to generate resonance in the direct current distribution network according to the output voltage, the output current, the impedance characteristic and the harmonic characteristic.
4. The method of claim 1, wherein the obtaining the resonant frequency of the dc distribution network from the operating parameters comprises:
establishing a node admittance matrix of the direct current power distribution network under different preset frequencies according to the operation parameters to obtain a plurality of node admittance matrixes;
obtaining modal impedance of each node admittance matrix to obtain a plurality of modal impedances;
and acquiring the resonant frequency of the direct current distribution network according to the magnitude relation of the modal impedances.
5. The method according to claim 1, wherein the obtaining the participation factor of each converter in the dc power distribution network corresponding to the resonant frequency comprises:
acquiring a node admittance matrix of the direct current distribution network corresponding to the resonance frequency, recording the node admittance matrix as a first node admittance matrix, and acquiring a node voltage matrix and an injection current matrix of the direct current distribution network corresponding to the node voltage matrix and the injection current matrix;
obtaining a modal voltage vector and a modal current vector according to the first node admittance matrix, the node voltage matrix and the injection current matrix;
and acquiring participation factors of each converter according to the modal voltage vector and the modal current vector.
6. The method of claim 1, wherein the active damping parameter adjustment is expressed by the following equation:
Z＝1-RaIo，
wherein Z is an active damping parameter, RaTo adjust the coefficients, IoIs the output current of the converter to be regulated.
7. The method of claim 1, wherein the combined adjustment of the active damping parameters and the virtual grid parameters comprises:
adjusting the active damping parameters of each converter to be adjusted, and injecting virtual power grid parameters into each converter to be adjusted so as to enable the resonant frequency of all the converters to be adjusted to be the same fixed resonant frequency and suppress the same fixed resonant frequency.
8. An oscillation suppression device for a direct current power distribution network, comprising:
the parameter acquisition module is used for acquiring operation parameters of each converter in the direct-current power distribution network, wherein the operation parameters comprise output voltage, output current, impedance characteristics and harmonic characteristics;
the resonance generation acquisition module is used for acquiring a converter set which is easy to generate resonance in the direct current power distribution network according to the operation parameters; obtaining a converter set which is easy to generate resonance in the direct current distribution network according to the operation parameters, wherein the converter set comprises: acquiring the resonant frequency of the direct current distribution network according to the operation parameters; acquiring participation factors of each converter in the direct-current power distribution network corresponding to the resonant frequency; determining a converter set which is easy to generate resonance according to the magnitude relation of the participation factors; determining a converter set which is easy to generate resonance according to the magnitude relation of the participation factors, wherein the converter set comprises: acquiring the maximum value of the participation factor; judging whether the absolute value of the difference value between the residual participation factor and the maximum value is smaller than a preset threshold value or not; if yes, the converter corresponding to the participation factor is included in the converter set;
and the oscillation suppression module is used for selecting a corresponding parameter adjustment mode according to the number of the converters in the converter set, if the number is one, the parameter adjustment mode is an active damping parameter adjustment mode, if the number is two or more, the parameter adjustment mode is an adjustment mode combining active damping parameters and virtual power grid parameters, and adjusting the parameters of each converter in the converter set according to the selected parameter adjustment mode so as to suppress oscillation of the direct-current power distribution network.
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