CN109494722B - Power grid side equivalent impedance modeling method and system - Google Patents

Power grid side equivalent impedance modeling method and system Download PDF

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CN109494722B
CN109494722B CN201811385751.4A CN201811385751A CN109494722B CN 109494722 B CN109494722 B CN 109494722B CN 201811385751 A CN201811385751 A CN 201811385751A CN 109494722 B CN109494722 B CN 109494722B
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voltage source
model
impedance
static var
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CN109494722A (en
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朱淼
徐莉婷
侯川川
蔡旭
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Shanghai Jiaotong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/10—Flexible AC transmission systems [FACTS]

Abstract

The invention provides a power grid side equivalent impedance modeling method and a system, comprising the following steps: polymerization equivalent step: taking a grid-connected admittance model of a single voltage source type static var compensator as a minimum modeling unit, and carrying out aggregation equivalence on the grid-connected admittance models of the multiple voltage source type static var compensators; establishing an equivalent impedance model: and establishing a power grid side equivalent impedance model containing a plurality of voltage source type static var compensators for operation by utilizing the coupling and impedance relation between the grid-connected admittance model of the voltage source type static var compensator and the line admittance model. An accurate and highly linear admittance model is established, and the effectiveness of a plurality of VSC-type STATCOM grid-connected admittance models is verified theoretically; the impedance characteristic of the existing line model is corrected by using the power grid side equivalent impedance obtained by the numerical relation between the admittance and the impedance and considering the operation of the VSC type STATCOM, and the impedance reference is favorably provided for the stability problem of new energy grid connection.

Description

Power grid side equivalent impedance modeling method and system
Technical Field
The invention relates to the field of alternating current power transmission and distribution, in particular to a power grid side equivalent impedance modeling method and system considering a voltage source type (VSC) static var compensator (STATCOM).
Background
With the increasing exhaustion of traditional energy sources such as coal, petroleum, natural gas and the like and the serious environmental problems caused by the exhaustion, the popularization, development and utilization of renewable energy sources become important means for solving the energy problems at the present stage. In China, tens of millions of kilowatt-level wind power/photovoltaic bases are built in the three north area, and extra-high voltage direct current is sent out to serve as the leading form of the development and utilization of the current renewable energy in China. The direct current transmission system of the renewable energy power generation base comprises diversified equipment such as wind-solar power generation, reactive compensation, direct current transmission, a synchronous generator and the like, the capacity of power electronic equipment is far larger than that of the synchronous generator, the effective inertia of the system is low, the short-circuit ratio is small, and the system can generate the oscillation problem of several Hz to several hundred Hz for many times. At present, the direct current transmission end wind power base of the Xinjiang renewable energy base which is put into operation has a lot of problems due to system oscillation, and even the thermal power generating unit is caused to trip.
The scale and the capacity of the distributed power generation system are continuously enlarged, the control strategy is increasingly complex, the diversified equipment has multi-time-scale voltage power angle coupling, the dynamic characteristics of the renewable energy power generation equipment are different from those of the traditional synchronous generator, and the transient behavior evolution rule of the direct current delivery system of the renewable energy power generation base is complicated due to the characteristics. At this time, the interaction between the grid-connected inverter and the interaction between the grid-connected inverter and the power grid become more obvious, and the complex oscillation problem is more easily caused, so that the stable operation of the power grid system is threatened.
Aiming at the problem generated by new energy grid connection, the current strategy is to change the total machine-grid impedance at the oscillation frequency by controlling the output impedance characteristic of equipment, and the current strategy comprises new energy base multi-type equipment impedance characteristic optimization and multi-equipment coordinated oscillation suppression of an active control device. When the impedance analysis method is used for researching the impedance stability of the grid-connected inverter and a power grid interactive system, the two subsystems are regarded as two independent subsystems, an impedance model is respectively established according to respective control structures and parameter characteristics, an equivalent circuit of the interactive system is represented by a linear network structure, and then the impedance stability criterion is adopted to analyze the system stability. The existing impedance analysis research of a grid-connected system directly equates the impedance of a power grid side to the line reactance ZgThe principle of the grid-connected system impedance analysis is shown in fig. 1. The impedance change caused by a reactive power compensation device (such as a VSC type STATCOM) in the line transmission process is neglected in the equivalent of the power grid side impedance, and the equivalent model of the impedance change deviates from the actual working condition. Under the conditions of various equipment control modes, complex network architecture and dynamic interaction among equipment, the traditional power grid side impedance equivalent model needs to be improved urgently.
In summary, due to the wide distribution of new energy, there are long transmission lines and necessary transformer equipment and reactive compensation devices (such as VSC type STATCOM) between the source and the grid and the load, and the grid-side impedance becomes a significant factor that is not negligible when viewed from the grid-connected side of the new energy.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a power grid side equivalent impedance modeling method and system.
The invention provides a power grid side equivalent impedance modeling method, which comprises the following steps:
polymerization equivalent step: taking a grid-connected admittance model of a single voltage source type static var compensator as a minimum modeling unit, and carrying out aggregation equivalence on the grid-connected admittance models of the multiple voltage source type static var compensators;
establishing an equivalent impedance model: and establishing a power grid side equivalent impedance model containing a plurality of voltage source type static var compensators for operation by utilizing the coupling and impedance relation between the grid-connected admittance model of the voltage source type static var compensator and the line admittance model.
Preferably, the polymerization equivalent step comprises:
and carrying out harmonic linearization on a phase-locked loop and a current loop control loop of the small signal of the voltage source type static var compensator in a frequency domain, obtaining current response caused by power grid voltage disturbance in an operating state by using a harmonic linearization result, and further calculating a grid-connected admittance model of the voltage source type static var compensator.
Preferably, the polymerization equivalent step further comprises:
the method comprises the following steps of carrying out aggregation equivalence on grid-connected admittance models of n voltage source type static var compensators, wherein the aggregation equivalence principle of the n voltage source type static var compensators is as follows: the capacity of the polymerization model is the sum of n voltage source type static var compensators, and the output current after polymerization is enlarged by n times; the filter inductance is reduced by n times; reducing the PI parameter of the current controller by n times; the input and output quantities of the phase-locked loop are not changed before and after the aggregation, and the control parameters are still set according to the single voltage source type static var compensator.
Preferably, the step of establishing the equivalent impedance model includes:
the existing network side impedance model is simplified into a Norton equivalent circuit, namely a power grid voltage source VgIs converted into a current source IgAnalyzing value Y by using grid-connected admittance model of a plurality of voltage source type static var compensatorsSTATCOMThe numerical relationship with the existing grid impedance model can be found as follows:
Figure BDA0001872910710000021
in the formula YgeThe impedance is written in the form of admittance of equivalent impedance at the power grid side as follows:
Figure BDA0001872910710000031
in the formula ZgeTo account for the grid-side equivalent impedance of the operation of a plurality of voltage source type static var compensators.
The invention provides a power grid side equivalent impedance modeling system, which comprises:
and (3) aggregation equivalent modules: taking a grid-connected admittance model of a single voltage source type static var compensator as a minimum modeling unit, and carrying out aggregation equivalence on the grid-connected admittance models of the multiple voltage source type static var compensators;
an equivalent impedance model establishing module: and establishing a power grid side equivalent impedance model containing a plurality of voltage source type static var compensators for operation by utilizing the coupling and impedance relation between the grid-connected admittance model of the voltage source type static var compensator and the line admittance model.
Preferably, the aggregate equivalent module includes:
and carrying out harmonic linearization on a phase-locked loop and a current loop control loop of the small signal of the voltage source type static var compensator in a frequency domain, obtaining current response caused by power grid voltage disturbance in an operating state by using a harmonic linearization result, and further calculating a grid-connected admittance model of the voltage source type static var compensator.
Preferably, the aggregate equivalence module further comprises:
the method comprises the following steps of carrying out aggregation equivalence on grid-connected admittance models of n voltage source type static var compensators, wherein the aggregation equivalence principle of the n voltage source type static var compensators is as follows: the capacity of the polymerization model is the sum of n voltage source type static var compensators, and the output current after polymerization is enlarged by n times; the filter inductance is reduced by n times; reducing the PI parameter of the current controller by n times; the input and output quantities of the phase-locked loop are not changed before and after the aggregation, and the control parameters are still set according to the single voltage source type static var compensator.
Preferably, the equivalent impedance model establishing module includes:
the existing network side impedance model is simplified into a Norton equivalent circuit, namely a power grid voltage source VgIs converted into a current source IgAnalyzing value Y by using grid-connected admittance model of a plurality of voltage source type static var compensatorsSTATCOMThe numerical relationship with the existing grid impedance model can be found as follows:
Figure BDA0001872910710000032
in the formula YgeThe impedance is written in the form of admittance of equivalent impedance at the power grid side as follows:
Figure BDA0001872910710000033
in the formula ZgeTo account for the grid-side equivalent impedance of the operation of a plurality of voltage source type static var compensators.
Compared with the prior art, the invention has the following beneficial effects:
1. the grid-connected admittance of a single VSC-type STATCOM is taken as a minimum modeling unit, phase-locked loops and current loop control parameters are calculated, an accurate and highly linear admittance model is established, and the effectiveness of a plurality of VSC-type STATCOM grid-connected admittance models is verified theoretically;
2. the coupling of the grid-connected admittance model of the VSC-type STATCOM and the existing power grid side impedance model is considered, the power grid side equivalent impedance which is obtained by using the numerical relation of admittance and impedance and accounts for the operation of the plurality of VSC-type STATCOMs is utilized, the impedance characteristic of the existing line model is corrected, and the impedance reference is favorably provided for the stability problem of new energy grid connection.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic diagram of grid-connected system impedance analysis;
FIG. 2 is a schematic diagram of a grid-side equivalent impedance that accounts for a STATCOM;
FIG. 3 is a block diagram of a PLL control loop;
FIG. 4 is a block diagram of a current control loop;
FIG. 5 is a schematic diagram of grid-connected admittance of a plurality of VSC-type STATCOMs;
FIG. 6 is a schematic diagram of a grid-side equivalent impedance that accounts for multiple STATCOMs;
FIG. 7 is a frequency characteristic curve of a conventional grid-side impedance model;
FIG. 8 is a frequency characteristic curve of a VSC type STATCOM grid-connected admittance model;
fig. 9 is a power grid side impedance model frequency characteristic curve taking into account grid connection of a plurality of VSC-type STATCOM.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 2, the method for modeling the equivalent impedance of the power grid side provided by the present invention includes:
polymerization equivalent step: taking a grid-connected admittance model of a single voltage source type static var compensator as a minimum modeling unit, and carrying out aggregation equivalence on the grid-connected admittance models of the multiple voltage source type static var compensators;
establishing an equivalent impedance model: and establishing a power grid side equivalent impedance model containing a plurality of voltage source type static var compensators for operation by utilizing the coupling and impedance relation between the grid-connected admittance model of the voltage source type static var compensator and the line admittance model.
In FIG. 2, ZgThe impedance on the power grid side is equivalent to the impedance of a transmission line in the traditional method, and the value of the impedance is equal to the reactance of the transmission line; y isSTATCOMThe grid-connected admittance of a plurality of VSC-type STATCOMs is determined by the number of the STATCOMs and a grid-connected admittance model of a single VSC-type STATCOM; vgIs the grid voltage; i isgIs the current of the power grid; zgeTo account for the grid side equivalent impedance of multiple VSC-type STATCOM operation.
Compared with the existing power grid impedance equivalent method, fig. 2 shows that the power grid side equivalent impedance technical scheme applied by the patent has line impedance Z on the traditional power grid sidegOn the basis, the actual operation condition of a power grid is taken as a modeling basis, and the introduction of a plurality of VSC-type STATCOMs into grid connection is consideredAdmittance Y ofSTATCOMTherefore, the power grid side equivalent impedance model is closer to the real power grid side impedance, and the deviation between the model and the actual power grid operation condition is reduced. The concrete implementation means is as follows:
A. single VSC type STATCOM grid-connected admittance model
The single VSC type STATCOM grid-connected admittance model is the minimum modeling unit in the scheme, the STATCOM is in a stable working state in the modeling process, harmonic linearization is carried out on each control link (a phase-locked loop and a current loop control loop) of a STATCOM small signal in a frequency domain, current response caused by power grid voltage disturbance in the STATCOM running state is obtained by utilizing the linearization result, and then the grid-connected admittance model of the STATCOM is calculated.
The PLL control loop is shown in FIG. 3, and when the input fundamental voltage contains positive sequence harmonic disturbance, the input voltage can be written as (for example, phase A)
Figure BDA0001872910710000051
Wherein v isaIs instantaneous value of A phase voltage, V1Is the fundamental voltage amplitude, ω1At fundamental voltage angular frequency, VpIs the harmonic voltage amplitude, omegapIn order to be at the harmonic voltage angular frequency,
Figure BDA0001872910710000052
is the initial phase of the harmonic voltage. The control loop indicates that the phase angle of the output of the phase-locked loop is thetaPLLOutput of coordinate transformation v without taking phase angle perturbation into accountd0、vq0By fundamental positive-sequence voltage phase angle theta only0Composition, taking into account perturbation phase angle delta theta corresponding to harmonic voltage componentPLLCan be expressed as
θPLL＝θ0+Δθ
The perturbation phase angle Delta theta and the fundamental wave phase angle theta are compared0Separated to obtain
Figure BDA0001872910710000053
Wherein
Figure BDA0001872910710000054
Neglecting the influence of high-order infinitesimal nonlinear components, the perturbation phase angle delta theta is approximated in the frequency domain
cos(θPLL)[f]＝cos(θ0)[f]-(Δθ·sinθ0)[f]
Wherein [ f ] is a frequency domain mark (the same below), the phase-locked loop can know that the influence of high-order infinitesimal nonlinear components is ignored when the perturbation phase angle delta theta is considered, and the q-axis voltage output by the coordinate transformation is approximate to be in a frequency domain
Figure BDA0001872910710000061
Wherein VqIs a component of the q-axis of the voltage, Gp(s) is a transfer function between harmonic voltage disturbances and the sum perturbation phase angle Δ θ, fpIs the harmonic frequency, f1Is the fundamental frequency. Furthermore, the control loop of the phase-locked loop can be seen
Δθ[f]＝HPLL（s）Vq[f]
Wherein HPLLRepresenting the transfer function of the phase-locked loop, of
HPLL(s)＝(kpp+kpi/s)/s
In the formula kppIs a phase-locked loop proportionality coefficient, kpiIs the phase locked loop integral coefficient. Combining the above expressions, the transfer function G between the positive sequence harmonic voltage disturbance and the perturbation phase angle delta theta can be obtainedp(s) is
Figure BDA0001872910710000062
Wherein D(s) is a transmission coefficient, which can be written as
Figure BDA0001872910710000063
When d axis and network voltage baseWhen the wave positive sequence components are overlapped, the d-axis current of the converter is active current, and the reference value is Idref(ii) a The q-axis current being a reactive current, reference value IqrefThe current loop control loop is shown in fig. 4. Neglecting the high order infinitesimal nonlinear component, I, when considering the lock perturbation phase angle Delta thetad、IqIn the frequency domain, different frequency components can be written as
Figure BDA0001872910710000064
In the formula VpTo disturb the voltage, I1Is a fundamental current, IpHarmonic currents output by VSC converters, IdIs d-axis current, IqIs the q-axis current, and is,
Figure BDA0001872910710000065
is the power factor angle. As can be seen from FIG. 4, in the steady state operation, the output of the fundamental current of the converter is equal to the reference current value, and H is in the current control loopi(s) the output value is constant, and the d-axis output steady-state value can be used as CdIndicating that the q-axis output steady state value can be CqAnd (4) showing. The output voltage of the converter is obtained according to the control loop
Figure BDA0001872910710000071
In the formula KdqTo decouple coefficients, EdD-axis voltage output by VSC converter, EqQ-axis voltage output by VSC converter, Hi(s) is the PI transfer function of the current loop. After the above formula is changed to a three-phase coordinate form, taking phase a as an example, the output voltage of the converter can be written as
Figure BDA0001872910710000072
EaFor the A-phase voltage output by the VSC converter, the converter grid-connected topology and a current control loop H are utilizedi(s) the output value is obtained
Figure BDA0001872910710000073
The converter is operating steadily Hi(s) output Cd、CqIs composed of
Figure BDA0001872910710000074
L is STATCOM filter inductance, when the grid voltage is injected into the disturbance frequency, the grid-connected topology of the VSC type STATCOM is utilized, and the positive sequence harmonic component is calculated under the disturbance frequency, so that the grid-connected topology can be obtained
Figure BDA0001872910710000075
The relationship between the positive sequence harmonic voltage and the harmonic current of the VSC-type STATCOM can be abbreviated as
Ip＝-YSTATCOM·Vp
Wherein Y isSTATCOMThe analytic value of the VSC type STATCOM grid-connected admittance model is
Figure BDA0001872910710000081
Therefore, a single VSC-type STATCOM grid-connected admittance model can be obtained, the model considers a steady-state operation value, a current control loop parameter, a phase-locked loop parameter, a voltage harmonic component and a current harmonic component, and frequency characteristic analysis of the single VSC-type STATCOM grid-connected admittance model is shown in an implementation example 1.
B. Grid-connected admittance model of multiple VSC type STATCOMs
The capacity of a single VSC-type STATCOM is limited, reactive compensation capacity can be improved by increasing the grid-connected quantity of the VSC-type STATCOM, and at the moment, the grid-connected admittance model of a plurality of VSC-type STATCOMs is inevitably influenced by the grid-connected quantity of the VSC-type STATCOMs. FIG. 5 is a schematic diagram of grid-connected admittance of a plurality of VSC-type STATCOMs, assuming that there are n VSC-type STATCOMs of the same type, wherein Y isSTATCOM1To YSTATCOMnFor single machine admittance, Y, of each STATCOMSTATCOMTotality of n VSC-type STATCOMsAnd (4) body grid-connected admittance. According to the scheme, the influence of control parameters such as phase-locked loops, current loops and the like is considered for the grid-connected admittance model of the VSC-type STATCOMs, and the models of the VSC-type STATCOMs are aggregated. The equivalent principle of aggregation of n STATCOMs is as follows: the capacity of the aggregation model VSC converter is the sum of n STATCOMs, namely the output current of the aggregated STATCOMs is enlarged by n times; the filter inductance is reduced by n times; reducing the PI parameter of the current controller by n times; the input and output quantities of the phase-locked loop are not changed before and after aggregation, and the control parameters are still set according to a single VSC type STATCOM. According to the analytic value of the grid-connected admittance model of a single VSC-type STATCOM, the harmonic voltage and current of a plurality of polymerized VSC-type STATCOMs can be written as
Figure BDA0001872910710000082
In the formula, lambda is a proportionality coefficient, and a plurality of VSC type STATCOM grid-connected polymerization admittance model analytic values Y can be obtainedSTATCOMIs composed of
Figure BDA0001872910710000083
The above formula shows that the grid-connected admittance of the multiple VSC-type STATCOMs in the scheme is related to the grid-connected number n of the STATCOMs and a single VSC-type STATCOM grid-connected admittance model. As can be seen from the analytic expression of the collective admittance model, the VSC-type STATCOM grid-connected admittance models are equivalent to the STATCOM grid-connected admittance collective model. According to the method, the control parameters of the phase-locked loop and the current loop are taken into consideration, a single VSC-type STATCOM is used for constructing a single-unit-level accurate admittance model, the high equivalence of a plurality of VSC-type STATCOM grid-connected admittance aggregation models is verified from a theoretical analytic formula, and the quick calculation of the plurality of VSC-type STATCOM grid-connected operation admittance models is facilitated.
C. Grid-side equivalent impedance considering multiple VSC type STATCOM grid-connected admittance and line impedance
Grid-connected admittance Y from multiple VSC type STATCOMsSTATCOMAccording to the model analysis expression, when the grid-connected operation of a plurality of VSC type STATCOMs is considered, YSTATCOMThe value of (c) is not negligible. In order to accurately model the equivalent impedance of the power grid side, fig. 2 can be simplified into a diagram according to the impedance analysis theory6. The existing network side impedance model is simplified into a Norton equivalent circuit and a power grid voltage source VgIs converted into a current source IgThe numerical relation between the grid-connected admittance model of the VSC type STATCOM and the existing power grid impedance model can be used for obtaining
Figure BDA0001872910710000091
In the formula YgeIn the form of admittance of equivalent impedance at power grid side, the impedance is written as
Figure BDA0001872910710000092
In the formula ZgeTo account for the grid side equivalent impedance of multiple VSC-type STATCOM operation. The frequency characteristic of the existing power grid side impedance model and the frequency characteristic of the power grid side equivalent impedance model considering a plurality of VSC type STATCOM grid-connected admittances are compared and analyzed in an implementation example 1.
Example 1:
the existing power grid side impedance model only considers line impedance, and changes along with the line impedance when a reactive power compensation device containing a plurality of VSC-type STATCOMs is connected to a grid. According to the scheme, the existing power grid side impedance model, the VSC-type STATCOM grid-connected admittance model and the frequency characteristic curves of the power grid side model considering the operation of the plurality of VSC-type STATCOMs are respectively drawn, and the correction of the existing power grid side impedance model by the scheme is verified by analyzing the three frequency characteristic curves. Because the invention aims to provide the reference of the impedance characteristic at the grid side for the stability problem of the new energy grid connection, only the low-frequency characteristic (0-130 Hz) in the frequency curve is compared in the implementation example.
According to the existing power grid side equivalent impedance modeling method, the line reactance is an equivalent impedance model, and the frequency characteristic curve of the power grid side impedance model is shown in fig. 7. In a logarithmic scale, the amplitude of the impedance on the power grid side is increased in proportion to the frequency in the graph, and the phase is constant. And drawing a frequency characteristic curve of the VSC-type STATCOM grid-connected admittance model by using an analytical expression of the VSC-type STATCOM grid-connected admittance model, wherein the frequency characteristic curve of the grid-connected admittance in the graph has obvious fluctuation between 30Hz and 130Hz, as shown in FIG. 8.
Fig. 9 is a frequency characteristic curve of a power grid side impedance model considering operation of a plurality of VSC-type STATCOM, and is almost consistent with an existing power grid side impedance model at 0 to 30Hz, as compared with fig. 7. After the grid-connected operation of a plurality of VSC-type STATCOMs is considered, the frequency characteristic curve of the impedance model on the power grid side fluctuates between 30Hz and 130Hz under the influence of the characteristics of the VSC-type STATCOMs. The frequency response of the impedance model shows: after the VSC-type STATCOM is considered to be connected to the grid, the deviation of the traditional model is reduced in partial frequency bands by the power grid side impedance model.
On the basis of the power grid side equivalent impedance modeling method, the invention also provides a power grid side equivalent impedance modeling system, which comprises the following steps:
and (3) aggregation equivalent modules: taking a grid-connected admittance model of a single voltage source type static var compensator as a minimum modeling unit, and carrying out aggregation equivalence on the grid-connected admittance models of the multiple voltage source type static var compensators;
an equivalent impedance model establishing module: and establishing a power grid side equivalent impedance model containing a plurality of voltage source type static var compensators for operation by utilizing the coupling and impedance relation between the grid-connected admittance model of the voltage source type static var compensator and the line admittance model.
Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, units provided by the present invention as pure computer readable program code, the system and its various devices, modules, units provided by the present invention can be fully implemented by logically programming method steps in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system and various devices, modules and units thereof provided by the invention can be regarded as a hardware component, and the devices, modules and units included in the system for realizing various functions can also be regarded as structures in the hardware component; means, modules, units for performing the various functions may also be regarded as structures within both software modules and hardware components for performing the method.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (4)

1. A power grid side equivalent impedance modeling method is characterized by comprising the following steps:
polymerization equivalent step: taking a grid-connected admittance model of a single voltage source type static var compensator as a minimum modeling unit, and carrying out aggregation equivalence on the grid-connected admittance models of the multiple voltage source type static var compensators;
establishing an equivalent impedance model: establishing a power grid side equivalent impedance model containing a plurality of voltage source type static var compensators for operation by utilizing the coupling and impedance relation between a grid-connected admittance model and a line admittance model of the voltage source type static var compensator;
the polymerization equivalent step comprises:
carrying out harmonic linearization on a phase-locked loop and a current loop control loop of a small signal of the voltage source type static var compensator in a frequency domain, obtaining current response caused by power grid voltage disturbance in an operating state by utilizing a harmonic linearization result, and further calculating a grid-connected admittance model of the voltage source type static var compensator;
the polymerization equivalent step further comprises:
the method comprises the following steps of carrying out aggregation equivalence on grid-connected admittance models of n voltage source type static var compensators, wherein the aggregation equivalence principle of the n voltage source type static var compensators is as follows: the capacity of the polymerization model is the sum of n voltage source type static var compensators, and the output current after polymerization is enlarged by n times; the filter inductance is reduced by n times; reducing the PI parameter of the current controller by n times; the input and output quantities of the phase-locked loop are not changed before and after the aggregation, and the control parameters are still set according to the single voltage source type static var compensator.
2. The power grid-side equivalent impedance modeling method of claim 1, wherein the equivalent impedance model building step comprises:
the existing network side impedance model is simplified into a Norton equivalent circuit, namely a power grid voltage source VgIs converted into a current source IgAnalyzing value Y by using grid-connected admittance model of a plurality of voltage source type static var compensatorsSTATCOMThe numerical relationship with the existing grid impedance model can be found as follows:
Figure FDA0002530346670000011
in the formula YgeIn the form of admittance of the grid-side equivalent impedance, ZgFor the traditional grid side line impedance, the impedance form is written as:
Figure FDA0002530346670000012
in the formula ZgeTo account for the grid-side equivalent impedance of the operation of a plurality of voltage source type static var compensators.
3. A grid-side equivalent impedance modeling system, comprising:
and (3) aggregation equivalent modules: taking a grid-connected admittance model of a single voltage source type static var compensator as a minimum modeling unit, and carrying out aggregation equivalence on the grid-connected admittance models of the multiple voltage source type static var compensators;
an equivalent impedance model establishing module: establishing a power grid side equivalent impedance model containing a plurality of voltage source type static var compensators for operation by utilizing the coupling and impedance relation between a grid-connected admittance model and a line admittance model of the voltage source type static var compensator;
the aggregate equivalence module comprises:
carrying out harmonic linearization on a phase-locked loop and a current loop control loop of a small signal of the voltage source type static var compensator in a frequency domain, obtaining current response caused by power grid voltage disturbance in an operating state by utilizing a harmonic linearization result, and further calculating a grid-connected admittance model of the voltage source type static var compensator;
the aggregate equivalence module further comprises:
the method comprises the following steps of carrying out aggregation equivalence on grid-connected admittance models of n voltage source type static var compensators, wherein the aggregation equivalence principle of the n voltage source type static var compensators is as follows: the capacity of the polymerization model is the sum of n voltage source type static var compensators, and the output current after polymerization is enlarged by n times; the filter inductance is reduced by n times; reducing the PI parameter of the current controller by n times; the input and output quantities of the phase-locked loop are not changed before and after the aggregation, and the control parameters are still set according to the single voltage source type static var compensator.
4. The grid-side equivalent impedance modeling system of claim 3, wherein the equivalent impedance model building module comprises:
the existing network side impedance model is simplified into a Norton equivalent circuit, namely a power grid voltage source VgIs converted into a current source IgAnalyzing value Y by using grid-connected admittance model of a plurality of voltage source type static var compensatorsSTATCOMThe numerical relationship with the existing grid impedance model can be found as follows:
Figure FDA0002530346670000021
in the formula YgeIn the form of admittance of the grid-side equivalent impedance, ZgFor the traditional grid side line impedance, the impedance form is written as:
Figure FDA0002530346670000022
in the formula ZgeTo account for the grid-side equivalent impedance of the operation of a plurality of voltage source type static var compensators.
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