CN111259565B - Dynamic simulation method and system for voltage source type current converter - Google Patents
Dynamic simulation method and system for voltage source type current converter Download PDFInfo
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Abstract
The invention provides a dynamic simulation method and a dynamic simulation system for a voltage source type current converter. The method is based on the principle of a multi-band dynamic vector method, and the dynamic vector model of the voltage source type current converter is decomposed, recombined and frequency-shifted to obtain the multi-band dynamic vector model; the simulation time is decomposed into a plurality of time subintervals according to the operating condition, and the simulation model and the window width of the windowed Fourier are selected for self-adaptive simulation according to the operating condition of the voltage source type converter in each time subinterval, so that different simulation models are adopted for self-adaptation of the steady-state operating condition and the fault operating condition. The invention combines the multi-band dynamic vector model with the self-adaptive variable simulation step length, solves the problems that the simulation scale and the simulation speed of the traditional VSC electromagnetic transient model are limited and the simulation precision cannot be ensured by the traditional VSC dynamic phasor model and a frequency offset method, and realizes the high-efficiency simulation which considers the steady-state working condition and the fault working condition and adopts the multi-band dynamic phasor model with different window widths.
Description
Technical Field
The invention relates to the technical field of converter performance research, in particular to a dynamic simulation method and system of a voltage source type converter.
Background
The large-scale access of new energy power generation and the wide construction of medium and low Voltage direct current transmission/distribution networks cause the operation mode of a power system to be deeply changed, and the transient characteristics of a grid-connected Voltage Source Converter (VSC) directly influence the dynamic characteristics of the power system containing the large-scale new energy power generation. The VSC has complex action characteristics, and the converter simulation model which can establish both precision and efficiency is always the focus content of academic research. Nowadays, a converter simulation model suitable for various occasions is established, such as a VSC detailed model, and the sampling theorem is used as a basis to capture the precise change of a high-frequency switch through an extremely small step length, but on one hand, the calculated amount is very large due to the excessively small step length, and on the other hand, the admittance array of the simulated power system must be updated during each switching action, so that the simulation burden is increased. The VSC dynamic vector model changes a high-frequency simulation object into a low-frequency simulation object through frequency shift, can perform simulation with a large step, but cannot consider harmonic waves, so that the precision of the model is reduced to a certain extent. VSC multifrequency section dynamic vector model, it is fixed to decompose the window width in windowing Fourier decomposition process, is power frequency cycle usually, consequently can not carry out step length self-adaptation according to the operating mode demand of difference, so how to realize giving consideration to the dynamic simulation of voltage source transverter of simulation speed and simulation accuracy becomes a technical problem that awaits the solution urgently. The method is used for solving the problem that the simulation scale and the simulation speed of the traditional VSC electromagnetic transient model are limited.
Disclosure of Invention
The invention aims to provide a dynamic simulation method and a dynamic simulation system for a voltage source type converter, which aim to solve the problems that the simulation scale and the simulation speed of the traditional VSC electromagnetic transient model are limited and the simulation precision cannot be ensured by the traditional VSC dynamic phasor model and a frequency offset method.
In order to achieve the purpose, the invention provides the following scheme:
a dynamic simulation method of a voltage source type converter comprises the following steps:
establishing a dynamic vector model of the voltage source type current converter;
decomposing, recombining and frequency shifting the dynamic vector model based on a multi-band dynamic vector method principle to obtain a multi-band dynamic vector model;
decomposing the simulation time into a plurality of time subintervals according to the operating condition;
based on the self-adaptive strategy principle, the window width of the multi-band dynamic phasor model is self-adaptively switched according to the working condition of the voltage type converter in each time subinterval, wherein the working condition is a steady-state working condition or a fault working condition;
and simulating each time subinterval by adopting the window width after each time subinterval is switched to realize the dynamic simulation of the voltage source type current converter.
Optionally, the establishing a dynamic vector model of the voltage source converter specifically includes:
the dynamic vector model of the voltage source type current converter is established as follows:
wherein t represents time, ua、ub、ucRespectively representing three-phase voltages at an outlet side of the voltage source type converter; i.e. ia、ib、icRespectively representing three-phase currents on the inlet side of the voltage source type converter; u. ofdThe voltage of the direct current side of the voltage source type converter is represented, and R and L respectively represent the equivalent resistance and the equivalent inductance of the coupling transformer at the alternating current side of the voltage source type converter; < > represents a dynamic vector; sa、Sb、ScRespectively representing the switching functions of a three-phase full bridge arm of the voltage source type converter;
optionally, the decomposing, recombining, and frequency shifting the dynamic vector model based on the principle of the multi-band dynamic vector method to obtain the multi-band dynamic vector model specifically includes:
based on the principle of a multi-band dynamic vector method, decomposing, recombining and frequency shifting the dynamic vector model to obtain the multi-band dynamic vector model is as follows:
wherein the content of the first and second substances,
respectively representing the sub-band dynamic phasors of the three-phase current signals at the inlet side of the voltage source type converter,
respectively representing the sub-band dynamic phasors of the three-phase voltage signal at the outlet side of the voltage source type converter,
and
respectively representing sub-frequency band dynamic phasors of switching function signals of a three-phase full bridge arm of the voltage source type converter;
wherein x (t) represents ia、ib、ic、ua、ub、uc、Sa、SbOr Sc；fnFrequency of the nth frequency band signal, BnRepresenting the nth frequency band signal, Hn-1And HnRespectively representing the last harmonic order, X, of the (n-1) th and nth frequency band signalsh(t) denotes the h-Fourier coefficient of x (t), ωhDenotes the angular frequency, ω, of the h-th harmonic of x (t)sAt the fundamental angular frequency, f (T)i) The window width when performing windowed fourier decomposition on the state vector of the ith time subinterval is shown, and x (τ) represents the signal over a period τ of x (t).
Optionally, decomposing the simulation time into a plurality of time subintervals according to the operating condition specifically includes:
decomposing the simulation time T into a plurality of time subintervals according to the operation condition as follows: t ═ T1∪T2∪T3∪……∪TI；T1、T2、T3And TIRespectively, the 1 st, 2 nd, 3 rd and I th time subintervals are indicated.
Optionally, based on the adaptive strategy principle, the window width of the multi-band dynamic phasor model is adaptively switched according to the working condition of the voltage-type converter in each time subinterval, where the working condition is a steady-state working condition or a fault working condition, and the method specifically includes:
when the voltage source type converter is in a steady-state working condition in the ith time subinterval, switching the window width of the windowed Fourier to a power frequency period; wherein, I is 1,2,3 …, and I represents the number of sub-time intervals;
and when the voltage source type converter is in a transient working condition in the ith time subinterval, switching the window width of the windowed Fourier to a switching period.
The invention also provides a dynamic simulation system of the voltage source type converter, which specifically comprises:
the dynamic vector model establishing module is used for establishing a dynamic vector model of the voltage source type current converter;
the multi-band dynamic vector model acquisition module is used for decomposing, recombining and frequency shifting the dynamic vector model based on a multi-band dynamic vector method principle to obtain a multi-band dynamic vector model;
the simulation time decomposition module is used for decomposing the simulation time into a plurality of time subintervals according to the operation working condition;
the adaptive window width switching module is used for adaptively switching the window width of the multi-band dynamic phasor model according to the working condition of the voltage type converter in each time subinterval based on an adaptive strategy principle, wherein the working condition is a steady-state working condition or a fault working condition;
and the simulation module is used for simulating each time subinterval by adopting the window width after each time subinterval is switched, so as to realize the dynamic simulation of the voltage source type current converter.
Optionally, the dynamic vector model establishing module specifically includes:
the dynamic vector model establishing submodule is used for establishing a dynamic vector model of the voltage source type current converter as follows:
wherein t represents time, ua、ub、ucRespectively representing three-phase voltages at an outlet side of the voltage source type converter; i.e. ia、ib、icRespectively representing three-phase currents on the inlet side of the voltage source type converter; u. ofdThe voltage of the direct current side of the voltage source type converter is represented, and R and L respectively represent the equivalent resistance and the equivalent inductance of the coupling transformer at the alternating current side of the voltage source type converter; < > represents a dynamic vector; sa、Sb、ScRespectively representing the switching functions of a three-phase full bridge arm of the voltage source type converter;
optionally, the multi-band dynamic vector model obtaining module specifically includes:
the multi-band dynamic vector model obtaining submodule is used for decomposing, recombining and frequency shifting the dynamic vector model based on the principle of a multi-band dynamic vector method to obtain the multi-band dynamic vector model, and comprises the following steps:
wherein the content of the first and second substances,
respectively representing the sub-band dynamic phasors of the three-phase current signals at the inlet side of the voltage source type converter,
respectively representing the sub-band dynamic phasors of the three-phase voltage signal at the outlet side of the voltage source type converter,
respectively representing sub-frequency band dynamic phasors of switching function signals of a three-phase full bridge arm of the voltage source type converter;
wherein x (t) represents ia、ib、ic、ua、ub、uc、Sa、SbOr Sc；fnFrequency of the nth frequency band signal, BnRepresenting the nth frequency band signal, Hn-1And HnRespectively representing the last harmonic order, X, of the (n-1) th and nth frequency band signalsh(t) denotes the h-Fourier coefficient of x (t), ωhDenotes the angular frequency, ω, of the h-th harmonic of x (t)sAt the fundamental angular frequency, f (T)i) The window width when performing windowed fourier decomposition on the state vector of the ith time subinterval is shown, and x (τ) represents the signal over a period τ of x (t).
Optionally, the simulation time decomposition module specifically includes:
the simulation time decomposition submodule is used for decomposing the simulation time T into a plurality of time subintervals according to the operation condition, and the time subintervals are as follows: t ═ T1∪T2∪T3∪……∪TI；T1、T2、T3And TIRespectively, the 1 st, 2 nd, 3 rd and I th time subintervals are indicated.
Optionally, the adaptive window width switching module specifically includes:
the first switching submodule is used for switching the window width of the windowed Fourier to a power frequency period when the voltage source type converter is in a steady-state working condition in the ith time subinterval; wherein, I is 1,2,3 …, and I represents the number of sub-time intervals;
and the second switching submodule is used for switching the window width of the windowed Fourier to a switching period when the voltage source type converter is in a transient working condition in the ith time subinterval.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a dynamic simulation method and a dynamic simulation system for a voltage source type current converter. Firstly, establishing a dynamic vector model of a voltage source type converter; decomposing, recombining and frequency shifting the dynamic vector model based on a multi-band dynamic vector method principle to obtain a multi-band dynamic vector model; then, the simulation time is decomposed into a plurality of time subintervals according to the operation working condition, and the windowing Fourier decomposition window width of the multi-band dynamic phasor is adaptively switched to perform simulation according to the working condition of the voltage source type current converter in each time subinterval based on the adaptive strategy principle. The invention combines a multi-band dynamic vector model with a self-adaptive variable simulation step length, solves the problems that the simulation scale and the simulation speed of the traditional VSC electromagnetic transient model are limited and the simulation precision cannot be ensured by the traditional VSC dynamic vector model and a frequency offset method, and realizes the dynamic simulation of the voltage source type converter which gives consideration to both the simulation speed and the simulation precision.
The method is based on the self-adaptive strategy principle, and the windowed Fourier window width is self-adaptively switched according to the steady-state working condition or the fault working condition of the voltage source type converter in each time subinterval, so that a simulation model giving consideration to the steady-state working condition and the fault working condition is adopted, and the dynamic simulation of the voltage source type converter giving consideration to the simulation speed and the simulation precision is realized; and the simulation is started after the corresponding window width is adopted after the switching is carried out on the specific working condition, so that the simulation precision is ensured and the simulation speed is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a flowchart of a dynamic simulation method of a voltage source converter according to the present invention;
fig. 2 is a topology structure diagram of the voltage source converter provided by the present invention;
FIG. 3 is a schematic diagram of a multi-band dynamic vector method provided by the present invention;
FIG. 4 is a schematic diagram of the band segmentation principle provided by the present invention;
fig. 5 is a schematic diagram illustrating the principle of the adaptive strategy provided by the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a dynamic simulation method and a dynamic simulation system for a voltage source type converter, which aim to solve the problems that the simulation scale and the simulation speed of the traditional VSC electromagnetic transient model are limited and the simulation precision cannot be ensured by the traditional VSC dynamic vector model and a frequency migration method.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
In order to achieve the above object, the present invention provides a dynamic simulation method of a voltage source converter, as shown in fig. 1, the simulation method includes the following steps:
the topological structure of the voltage source type converter is shown in fig. 2, and the dynamic vector model of the voltage source type converter established by the invention is as follows:
wherein t represents time, ua、ub、ucRespectively representing three-phase voltages at an outlet side of the voltage source type converter; i.e. ia、ib、icRespectively representing three-phase currents on the inlet side of the voltage source type converter; u. ofdThe voltage of the direct current side of the voltage source type converter is represented, and R and L respectively represent the equivalent resistance and the equivalent inductance of the coupling transformer at the alternating current side of the voltage source type converter; < > represents a dynamic vector; sa、Sb、ScRespectively representing the switching functions of a three-phase full bridge arm of the voltage source type converter;
and 102, decomposing, recombining and frequency shifting the dynamic vector model based on the principle of a multi-band dynamic vector method to obtain the multi-band dynamic vector model.
Based on the principle of a multi-band dynamic vector method, the invention decomposes, recombines and shifts the frequency of the dynamic vector model to obtain the multi-band dynamic vector model, which comprises the following steps:
wherein the content of the first and second substances,
respectively representing the sub-band dynamic phasors of the three-phase current signals at the inlet side of the voltage source type converter,
respectively representing the sub-band dynamic phasors of the three-phase voltage signal at the outlet side of the voltage source type converter,
and
respectively representing sub-frequency band dynamic phasors of switching function signals of a three-phase full bridge arm of the voltage source type converter;
wherein x (t) represents ia、ib、ic、ua、ub、uc、Sa、SbOr Sc；fnFrequency of the nth frequency band signal, BnRepresenting the nth frequency band signal, Hn-1And HnRespectively representing the last harmonic order, X, of the (n-1) th and nth frequency band signalsh(t) denotes the h-Fourier coefficient of x (t), ωhDenotes the angular frequency, ω, of the h-th harmonic of x (t)sAt the fundamental angular frequency, f (T)i) The window width when performing windowed fourier decomposition on the state vector of the ith time subinterval is shown, and x (τ) represents the signal over a period τ of x (t).
The principle of the multi-band dynamic vector method is shown in fig. 3, and includes the steps of decomposition, recombination and frequency shift.
The specific steps of signal decomposition and recombination are as follows: voltage, current, etc. in an electrical power system can be seen as periodically varying electrical signals. For period of T0In a period tau e (T-T) of a period x (tau)0,t]The fourier decomposition of its complex form is:
in the formula: x (t) is a complex form of the electrical signal x (τ), ωs＝2π/T0At fundamental angular frequency, Xh(t) is the h-th order Fourier transformThe leaf coefficient, i.e., the h-order "dynamic phasor".
The fourier coefficient h in the equation (1) is theoretically infinite, but in the electromagnetic transient simulation, the frequency corresponding to the simulation step length is generally 10 times of the signal frequency according to the requirements of precision and sampling theorem. Therefore, in electromagnetic transient simulation, the harmonic number h is generally finite, and the maximum value can be determined according to the simulation step size (for example, the maximum harmonic number h corresponding to the 50 μ s simulation step size is 40). At this time, formula (1) can be written as:
the mathematical meaning of the fourier transform is: any periodic signal satisfying the dirichlet condition can be represented as a group by ejhωstIs a linear combination of orthogonal bases. If the signal frequency is divided into N sub-bands according to fig. 4, by the linear combination law, equation (2) can be grouped and recombined according to the sub-bands, and the signals before and after combination are equal, which means the same signal x (t).
The result of each subband recombination is: a plurality of sub-signals with different frequencies obtained by Fourier decomposition in each frequency band are recombined into 1 frequency band signal. At this time, x (t) can be regarded as the sum of the signals of the frequency bands, that is:
wherein, Bn (t) is the recombined sub-band signal of the nth frequency band.
Comparing the terms on the right of the equations (2) and (3), it can be found that the term of the equation (2) is greatly reduced from the harmonic number 2M to the frequency band number 2N.
The signal frequency shift comprises the following steps: the complex signal X (t) is recombined in a segmented manner according to the frequency from small to large in the formula (3). For each sub-band signal bn (t), a frequency within a band (e.g., the center frequency of each band) may be selected to be shifted, respectively, that is:
wherein the content of the first and second substances,
for the signals after frequency shift of the sub-bands, it is abbreviated as
ωrnFor a frequency-shifted angular frequency of the frequency band n,
is the upper and lower frequency limits, f, of the frequency band nhIs the frequency of the signal in the frequency band and satisfies
Balance
Is the sub-frequency band dynamic phasor (SFB-DP) of the signal. Obviously, compared with the conventional dynamic phasor Xh(t) dynamic phasors for sub-bands differing by only one frequency component
Is a signal having a bandwidth. If the bandwidth satisfies the narrow-band condition, then
Is also a low-frequency signal, and large-step simulation can be adopted for the low-frequency signal, thereby improving the simulation speed.
When the traditional dynamic phasor method is used for electromagnetic transient simulation, signals are firstly decomposed into dynamic phasors of each order according to the formula (2), and then the dynamic phasors of each order are placed in different CPU cores for parallel simulation by utilizing the characteristics of CPU multi-core cores. However, because the number of CPU cores is limited, the traditional dynamic phasor method can only adopt a few orders of dynamic phasors to form an equation set for parallel simulation. Therefore, the total bandwidth of the signals simulated by the traditional dynamic phasor method is far smaller than the actual bandwidth of the signals, so that the harmonic truncation error is large and the simulation precision is low. Different from the traditional dynamic phasor method, if the frequency-shifted sub-band dynamic phasor is decomposed according to the formula (3) for parallel simulation, because the sub-band signal has a certain bandwidth, under the condition that the frequency-shifted sub-band dynamic phasor has the same equation set number as the traditional dynamic phasor method, the bandwidth of the simulatable signal is far greater than that of the traditional dynamic phasor method, and the harmonic truncation error is far less than that of the traditional dynamic phasor method, so that the simulatable signal has extremely high simulation precision.
103, decomposing the simulation time into a plurality of time subintervals according to the operation condition; the method specifically comprises the following steps:
decomposing the simulation time T into a plurality of time subintervals according to the operation condition as follows: t ═ T1∪T2∪T3∪……∪TI；T1、T2、T3And TIRespectively, the 1 st, 2 nd, 3 rd and I th time subintervals are indicated.
104, based on the self-adaptive strategy principle, self-adaptively switching the window width of the multi-band dynamic phasor model according to the working condition of the voltage type current converter in each time subinterval, wherein the working condition is a steady-state working condition or a fault working condition;
and 105, simulating each time subinterval by using the window width switched by each time subinterval to realize the dynamic simulation of the voltage source type current converter.
Specifically, when simulation is performed, if the converter is in a steady-state working condition, the VSC multi-band dynamic phasor model is applied on a power frequency cycle time scale, namely, when windowing Fourier decomposition is performed on the VSC multi-band dynamic phasor model, a power frequency cycle is used as a decomposition window width, and simulation is performed with a large step length. If the converter is disturbed (if a fault occurs), when the converter is in a transient working condition, the disturbance moment is advanced by a certain time quantum (the advanced time quantum is determined according to the actual simulation condition, and the advanced time quantum is 2T in the patentS，TSSwitching period), starting at a time after the time is advanced, applying a VSC multi-band dynamic phasor model on a switching period time scale, namely adopting the switching period as a decomposition window width when carrying out windowed Fourier decomposition on the VSC multi-band dynamic phasor model, and carrying out simulation by using small step length. If the simulation precision of the transient working condition of the converter is further improved, the rotating frequency of the multi-band dynamic vector can be zero, namely, a detailed model is adopted for simulation, and therefore extremely high simulation precision is obtained. FIG. 5 is a schematic diagram of an adaptive strategy for recovering a converter after the converter is disturbed and the operation condition changes.
The invention also provides a dynamic simulation system of the voltage source type converter, which specifically comprises:
and the dynamic vector model establishing module is used for establishing a dynamic vector model of the voltage source type current converter.
The dynamic vector model building module specifically comprises:
the dynamic vector model establishing submodule is used for establishing a dynamic vector model of the voltage source type current converter as follows:
wherein t represents time, ua、ub、ucRespectively representing three-phase voltages at an outlet side of the voltage source type converter; i.e. ia、ib、icRespectively representing three-phase currents on the inlet side of the voltage source type converter; u. ofdRepresenting the DC side voltage of a voltage source type converter, R and L representing the voltage source respectivelyThe AC side of the converter is connected with the equivalent resistance and the equivalent inductance of the transformer; < > represents a dynamic vector; sa、Sb、ScRespectively representing the switching functions of a three-phase full bridge arm of the voltage source type converter;
and the multi-band dynamic vector model acquisition module is used for decomposing, recombining and frequency shifting the dynamic vector model based on a multi-band dynamic vector method principle to obtain the multi-band dynamic vector model.
The multi-band dynamic vector model obtaining module specifically comprises:
the multi-band dynamic vector model obtaining submodule is used for decomposing, recombining and frequency shifting the dynamic vector model based on the principle of a multi-band dynamic vector method to obtain the multi-band dynamic vector model, and comprises the following steps:
wherein the content of the first and second substances,
respectively representing the sub-band dynamic phasors of the three-phase current signals at the inlet side of the voltage source type converter,
respectively representing the sub-band dynamic phasors of the three-phase voltage signal at the outlet side of the voltage source type converter,
respectively representing sub-frequency band dynamic phasors of switching function signals of a three-phase full bridge arm of the voltage source type converter;
wherein x (t) represents ia、ib、ic、ua、ub、uc、Sa、SbOr Sc；fnFrequency of the nth frequency band signal, BnRepresenting the nth frequency band signal, Hn-1And HnRespectively representing the last harmonic order, X, of the (n-1) th and nth frequency band signalsh(t) denotes the h-Fourier coefficient of x (t), ωhDenotes the angular frequency, ω, of the h-th harmonic of x (t)sAt the fundamental angular frequency, f (T)i) The window width when performing windowed fourier decomposition on the state vector of the ith time subinterval is shown, and x (τ) represents the signal over a period τ of x (t).
And the simulation time decomposition module is used for decomposing the simulation time into a plurality of time subintervals according to the operating condition.
The simulation time decomposition module specifically comprises: the simulation time decomposition submodule is used for decomposing the simulation time T into a plurality of time subintervals according to the operation condition, and the time subintervals are as follows: t ═ T1∪T2∪T3∪……∪TI； T1、T2、T3And TIRespectively, the 1 st, 2 nd, 3 rd and I th time subintervals are indicated.
And the self-adaptive window width switching module is used for self-adaptively switching the window width of the multi-band dynamic phasor model according to the working condition of the voltage type current converter in each time subinterval based on the self-adaptive strategy principle, wherein the working condition is a steady-state working condition or a fault working condition.
The self-adaptive window width switching module comprises a first switching submodule and is used for switching the window width of the windowed Fourier to a power frequency period when the voltage source type converter is in a steady-state working condition in the ith time subinterval; wherein, I is 1,2,3 …, and I represents the number of sub-time intervals; and the second switching submodule is used for switching the window width of the windowed Fourier to a switching period when the voltage source type converter is in a transient working condition in the ith time subinterval.
And the simulation module is used for simulating each time subinterval by adopting the window width after each time subinterval is switched, so as to realize the dynamic simulation of the voltage source type current converter.
The method and the system of the invention have the following advantages: the self-adaptive strategy idea of the invention can self-adaptively switch the window width of each variable windowing Fourier decomposition according to the requirements of different operation working conditions, and uses large step length simulation under the steady state working condition and small step length simulation under the transient state working condition. The self-adaptive strategy specific method adopts a large window width to carry out Fourier decomposition under the steady-state working condition, the window width can be amplified to a power frequency period and is far larger than the window widths of other methods, and the simulation speed is improved. And under the transient working condition, the switching period is used as the window width, so that the simulation precision is ensured. The VSC self-adaptive multi-band dynamic phasor electromagnetic transient simulation model organically combines a self-adaptive strategy and a multi-band dynamic phasor method, so that the window width of the multi-band dynamic phasor method is variable and is not fixed any more when the multi-band dynamic phasor method carries out windowed Fourier decomposition on variables, and the simulation speed and the simulation precision are considered at the same time.
Specifically, the VSC adaptive multi-band dynamic phasor electromagnetic transient simulation model is compared with a VSC traditional dynamic phasor model.
1) The VSC self-adaptive multi-band dynamic phasor electromagnetic transient simulation model is different from the VSC traditional dynamic phasor model, and when the system frequency fluctuates (such as low-frequency oscillation), the problem of frequency spectrum leakage of a dynamic phasor method cannot occur.
2) Because the frequency range of the VSC self-adaptive multi-band dynamic phasor electromagnetic transient simulation model research is very large, the problem of harmonic wave does not need to be considered independently, and the harmonic wave truncation error is very small.
2. The VSC self-adaptive multi-band dynamic phasor electromagnetic transient simulation model is compared with a VSC frequency offset method model.
1) Compared with a VSC frequency offset method model, the VSC self-adaptive multi-band dynamic phasor electromagnetic transient simulation model has the advantages that the dominant frequency is the frequency band center frequency, the degree of freedom of selection is high, the defect that the VSC frequency offset method model can only shift the frequency of signals nearby a power frequency fundamental wave is overcome, and the simulation precision is high.
2) The number of sets of differential equations established by the VSC self-adaptive multi-band dynamic phasor electromagnetic transient simulation model is equal to the number N of sub-bands, compared with a VSC frequency offset method model, the number of equations is slightly increased, and due to mutual independence among the sub-bands, the CPU multi-core technology can be utilized for parallel solution, so that the simulation calculation speed can be greatly increased.
3. The VSC self-adaptive multi-band dynamic phasor electromagnetic transient simulation model is compared with the VSC multi-band dynamic phasor model.
The windowed Fourier decomposition window width of the VSC self-adaptive multi-band dynamic phasor electromagnetic transient simulation model can be changed, the defect that the window width of the VSC multi-band dynamic phasor model is not changed (usually power frequency) is overcome, large-step simulation can be adopted under the steady-state working condition, small-step simulation can be adopted under the transient working condition, and both the simulation precision and the simulation speed are considered.
The equivalent embodiments in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts between the equivalent embodiments can be referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principle and the implementation manner of the present invention are explained by applying specific examples, the above description of the embodiments is only used to help understanding the method of the present invention and the core idea thereof, the described embodiments are only a part of the embodiments of the present invention, not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.
Claims (8)
1. A dynamic simulation method of a voltage source converter is characterized by comprising the following steps:
establishing a dynamic vector model of the voltage source type current converter;
decomposing, recombining and frequency shifting the dynamic vector model based on a multi-band dynamic vector method principle to obtain a multi-band dynamic vector model;
decomposing the simulation time into a plurality of time subintervals according to the operating condition;
based on the self-adaptive strategy principle, the window width of the multi-band dynamic phasor model is self-adaptively switched according to the working condition of the voltage source type converter in each time subinterval, wherein the working condition is a steady-state working condition or a fault working condition;
simulating each time subinterval by adopting the window width after each time subinterval is switched to realize the dynamic simulation of the voltage source type current converter;
based on the self-adaptive strategy principle, the window width of the multi-band dynamic phasor model is switched in a self-adaptive mode according to the working condition of the voltage source type current converter in each time subinterval, the working condition is a steady-state working condition or a fault working condition, and the method specifically comprises the following steps:
when the voltage source type converter is in a steady-state working condition in the ith time subinterval, switching the window width of the windowed Fourier to a power frequency period; wherein, I is 1,2,3 …, and I represents the number of sub-time intervals;
and when the voltage source type converter is in a transient working condition in the ith time subinterval, switching the window width of the windowed Fourier to a switching period.
2. The method according to claim 1, wherein the establishing a dynamic vector model of the voltage source converter specifically comprises:
the dynamic vector model of the voltage source type current converter is established as follows:
wherein t represents time, ua、ub、ucRespectively representing three-phase voltages at an outlet side of the voltage source type converter; i.e. ia、ib、icRespectively representing three-phase currents on the inlet side of the voltage source type converter; u. ofdRepresenting the DC side voltage of the voltage source converter, R and L respectively representing the AC side connection transformation voltage of the voltage source converterEquivalent resistance and equivalent inductance; < > represents a dynamic vector; sa、Sb、ScRespectively representing the switching functions of a three-phase full bridge arm of the voltage source type converter;
3. the method according to claim 2, wherein the decomposing, recombining and frequency shifting the dynamic vector model based on the multi-band dynamic vector method principle to obtain the multi-band dynamic vector model specifically comprises:
based on the principle of a multi-band dynamic vector method, decomposing, recombining and frequency shifting the dynamic vector model to obtain the multi-band dynamic vector model is as follows:
wherein the content of the first and second substances,
respectively representing the sub-band dynamic phasors of the three-phase current signals at the inlet side of the voltage source type converter,
respectively representing the sub-band dynamic phasors of the three-phase voltage signal at the outlet side of the voltage source type converter,
and
respectively representing sub-frequency band dynamic phasors of switching function signals of a three-phase full bridge arm of the voltage source type converter;
wherein x (t) represents ia、ib、ic、ua、ub、uc、Sa、SbOr Sc；fnFrequency of the nth frequency band signal, BnRepresenting the nth frequency band signal, Hn-1And HnRespectively representing the last harmonic order, X, of the (n-1) th and nth frequency band signalsh(t) denotes the h-Fourier coefficient of x (t), ωhDenotes the angular frequency, ω, of the h-th harmonic of x (t)sAt the fundamental angular frequency, f (T)i) The window width when performing windowed fourier decomposition on the state vector of the ith time subinterval is shown, and x (τ) represents the signal over a period τ of x (t).
4. The method according to claim 1, wherein the decomposing the simulation time into a plurality of time subintervals according to the operating condition specifically comprises:
decomposing the simulation time T into a plurality of time subintervals according to the operation condition as follows: t ═ T1∪T2∪T3∪……∪TI；T1、T2、T3And TIRespectively, the 1 st, 2 nd, 3 rd and I th time subintervals are indicated.
5. A dynamic simulation system of a voltage source converter is characterized by specifically comprising:
the dynamic vector model establishing module is used for establishing a dynamic vector model of the voltage source type current converter;
the multi-band dynamic vector model acquisition module is used for decomposing, recombining and frequency shifting the dynamic vector model based on a multi-band dynamic vector method principle to obtain a multi-band dynamic vector model;
the simulation time decomposition module is used for decomposing the simulation time into a plurality of time subintervals according to the operation working condition;
the self-adaptive window width switching module is used for self-adaptively switching the window width of the multi-band dynamic phasor model according to the working condition of the voltage source type converter in each time subinterval based on the self-adaptive strategy principle, wherein the working condition is a steady-state working condition or a fault working condition;
the simulation module is used for simulating each time subinterval by adopting the window width after each time subinterval is switched, so as to realize the dynamic simulation of the voltage source type current converter;
the adaptive window width switching module specifically includes:
the first switching submodule is used for switching the window width of the windowed Fourier to a power frequency period when the voltage source type converter is in a steady-state working condition in the ith time subinterval; wherein, I is 1,2,3 …, and I represents the number of sub-time intervals;
and the second switching submodule is used for switching the window width of the windowed Fourier to a switching period when the voltage source type converter is in a transient working condition in the ith time subinterval.
6. The dynamic simulation system of a voltage source converter according to claim 5, wherein the dynamic vector model building module specifically comprises:
the dynamic vector model establishing submodule is used for establishing a dynamic vector model of the voltage source type current converter as follows:
wherein t represents time, ua、ub、ucRespectively representing three-phase voltages at an outlet side of the voltage source type converter; i.e. ia、ib、icRespectively representing three-phase currents on the inlet side of the voltage source type converter; u. ofdThe voltage of the direct current side of the voltage source type converter is represented, and R and L respectively represent the equivalent resistance and the equivalent inductance of the coupling transformer at the alternating current side of the voltage source type converter; < > represents a dynamic vector; sa、Sb、ScRespectively representing voltage source type commutationSwitching functions of three-phase full bridge arms of the device;
7. the dynamic simulation system of a voltage source converter according to claim 6, wherein the multi-band dynamic vector model obtaining module specifically comprises:
the multi-band dynamic vector model obtaining submodule is used for decomposing, recombining and frequency shifting the dynamic vector model based on the principle of a multi-band dynamic vector method to obtain the multi-band dynamic vector model, and comprises the following steps:
wherein the content of the first and second substances,
respectively representing the sub-band dynamic phasors of the three-phase current signals at the inlet side of the voltage source type converter,
respectively representing the sub-band dynamic phasors of the three-phase voltage signal at the outlet side of the voltage source type converter,
and
respectively representing sub-frequency band dynamic phasors of switching function signals of a three-phase full bridge arm of the voltage source type converter;
wherein x (t) represents ia、ib、ic、ua、ub、uc、Sa、SbOr Sc；fnFrequency of the nth frequency band signal, BnRepresenting the nth frequency band signal, Hn-1And HnRespectively representing the last harmonic order, X, of the (n-1) th and nth frequency band signalsh(t) denotes the h-Fourier coefficient of x (t), ωhDenotes the angular frequency, ω, of the h-th harmonic of x (t)sAt the fundamental angular frequency, f (T)i) The window width when performing windowed fourier decomposition on the state vector of the ith time subinterval is shown, and x (τ) represents the signal over a period τ of x (t).
8. The dynamic simulation system of the voltage source converter according to claim 5, wherein the simulation time decomposition module specifically comprises:
the simulation time decomposition submodule is used for decomposing the simulation time T into a plurality of time subintervals according to the operation condition, and the time subintervals are as follows: t ═ T1∪T2∪T3∪……∪TI；T1、T2、T3And TIRespectively, the 1 st, 2 nd, 3 rd and I th time subintervals are indicated.
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