CN113471953A - Light storage direct current micro-grid modeling method - Google Patents

Light storage direct current micro-grid modeling method Download PDF

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CN113471953A
CN113471953A CN202110707462.7A CN202110707462A CN113471953A CN 113471953 A CN113471953 A CN 113471953A CN 202110707462 A CN202110707462 A CN 202110707462A CN 113471953 A CN113471953 A CN 113471953A
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direct
grid
converter
energy storage
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CN113471953B (en
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刘芳
汪浩东
李�昊
刘威
赵杨
凌淳扬
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Hefei University of Technology
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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
    • H02J1/10—Parallel operation of dc sources
    • 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
    • H02J1/14—Balancing the load in a network
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • 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
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • 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
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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Abstract

The invention relates to the field of light storage direct current micro-grids, and discloses a light storage direct current micro-grid modeling method. Meanwhile, the impedance model is not established in consideration of the direct-current microgrid at present, and the impedance modeling of the direct-current simulation power grid of the direct-current microgrid from the direct-current side is less and less. The method provides convenience for analyzing the stability of the whole optical storage direct current micro-grid system, and better realizes the application of impedance modeling in the optical storage direct current micro-grid.

Description

Light storage direct current micro-grid modeling method
Technical Field
The invention relates to the field of optical storage direct current micro-grids, and provides a modeling method for an optical storage direct current micro-grid.
Background
In recent years, with the rapid development of clean renewable energy technology, micro-grids have come into existence in order to improve the energy utilization rate and the reliability of power supply quality. Compared with an alternating-current microgrid, the direct-current microgrid has the advantages that the system is simpler and more flexible, the cost and the loss are lower, and the coordination control is easy. Therefore, it is necessary to analyze the stability of the optical storage dc microgrid system. At present, the types and the number of converters in the optical storage direct current microgrid system are more, and each converter is generally designed independently and then connected together to form the direct current microgrid system, so that mutual influences exist among the connected converters, and the influences directly influence the stability of the whole optical storage direct current microgrid system. Therefore, when a plurality of expert scholars study the stability of the whole direct current microgrid system, the optical storage direct current microgrid modeling provides some own methods:
the article entitled "hierarchical control of bus voltage of a direct current microgrid and small signal stability analysis", (university of western ann rationale, 2019) deduces an impedance model of an optical storage direct current microgrid system, however, the optical storage direct current microgrid system in the article does not have a direct current simulation power grid part, so that the direct current simulation power grid impedance modeling part does not exist, and the influence of the direct current simulation power grid part on the stability of the whole optical storage direct current microgrid system cannot be analyzed subsequently.
An article entitled "direct current microgrid stability analysis and damping control method research" ("Chinese Motor engineering Collection" 2016, volume 36, phase 4, 927-. The state space model depends on the integrity and the certainty of the whole microgrid system, once a certain unit in the system is changed, the whole microgrid system needs to be modeled again, and the impedance modeling only needs to be performed on the changed unit again.
An article entitled "stability analysis and experimental research of optical storage type direct current micro grid" (university of electronic technology, 2020) establishes a state space model of the optical storage direct current micro grid to analyze the stability of the whole system, and meanwhile, the system topology of the whole optical storage direct current micro grid mentioned in the article is not completely the same as the system topology in the text.
In summary, in analyzing the stability of the optical storage direct current microgrid system, at present, a few impedance models are considered to be established, and the impedance modeling of the direct current microgrid direct current analog power grid from the direct current side involves very little, which is very important for further researching the stability of the whole optical storage direct current microgrid system.
Disclosure of Invention
The invention aims to overcome the limitations of the various technical schemes and provides a light storage direct current microgrid modeling method aiming at considering a light storage direct current microgrid system.
The object of the invention is thus achieved. The invention provides a modeling method of an optical storage direct current micro-grid, wherein a topological structure of the optical storage direct current micro-grid comprises a photovoltaic converter structure, an energy storage converter structure and a direct current simulation power grid structure; the photovoltaic converter structure comprises photovoltaic cells PV of the photovoltaic converter and an input side capacitor C of the photovoltaic converterpvPhotovoltaic converter inductor LpvDiode VD of photovoltaic converterpvTriode S of photovoltaic converterpvAnd a photovoltaic converter output side capacitor Cdcpv(ii) a The energy storage converter structure comprises an energy storage Battery of the energy storage converter and an input side capacitor C of the energy storage converterb1Inductor L of energy storage converterbBoost triode S of energy storage converterb1Buck triode S of energy storage converterb2And the output side capacitor C of the energy storage converterb2(ii) a The DC simulation power grid structure comprises a DC side capacitor C of the DC simulation power griddcgTwo-level three-bridge-arm inverter M of direct-current analog power grid and arm-side three-phase inductor L of direct-current analog power bridge1Three-phase filter capacitor C of direct current analog power gridfNetwork side three-phase inductor L of direct current simulation power grid2Three-phase power grid impedance L of direct current simulation power gridgAnd a three-phase alternating current power grid e of the direct current simulation power grid; photovoltaic converter output side capacitor CdcpvEnergy storage conversionCapacitor C at output side of deviceb2DC side capacitor C of DC analog power griddcgThe three are connected in parallel;
the optical storage direct-current microgrid modeling method comprises the steps of establishing a direct-current microgrid photovoltaic converter impedance model, establishing a direct-current microgrid energy storage converter impedance model and establishing a direct-current microgrid direct-current simulation power grid impedance model, and specifically comprises the following steps:
step 1, establishing an impedance model of the direct-current micro-grid photovoltaic converter, wherein the impedance model comprises sampling and modeling, and the specific process comprises the following steps:
step 1.1, acquiring output current i of photovoltaic cell of photovoltaic converter through collectionpvAnd the inductive current i of the photovoltaic converterLpvAnd the capacitance voltage u at the input side of the photovoltaic converterCpvThe output side capacitor voltage u of the photovoltaic converterdcpvCurrent i at output side of photovoltaic converterdcpv；
Step 1.2, establishing a main circuit mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA0003130186730000031
in the formula:
Figure BDA0003130186730000032
output current i for photovoltaic cell of photovoltaic converterpvSmall signal component of steady-state operating point, ILpvFor the inductive current i of the photovoltaic converterLpvThe dc component of the steady-state operating point,
Figure BDA0003130186730000033
for the inductive current i of the photovoltaic converterLpvThe small signal component of the steady-state operating point,
Figure BDA0003130186730000034
for the input side capacitance voltage u of the photovoltaic converterCpvSmall signal component of steady state operating point, UdcpvFor the output side capacitor voltage u of the photovoltaic converterdcpvThe dc component of the steady-state operating point,
Figure BDA0003130186730000035
for the output side capacitor voltage u of the photovoltaic converterdcpvThe small signal component of the steady-state operating point,
Figure BDA0003130186730000036
for the output side current i of the photovoltaic converterdcpvSmall signal component of steady state operating point, DpvOpen loop duty cycle d for photovoltaic converterspvThe dc component of the steady-state operating point,
Figure BDA0003130186730000037
open loop duty cycle d for photovoltaic converterspvSmall signal component of steady state working point, s is Laplace operator;
step 1.3, establishing an open-loop impedance model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA0003130186730000038
in the formula: zopvOpen loop impedance for the photovoltaic converter;
step 1.4, establishing a voltage outer loop mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA0003130186730000039
in the formula:
Figure BDA00031301867300000310
controlling a voltage command u for a photovoltaic converter MPPTpvrefThe small signal component of the steady-state operating point,
Figure BDA00031301867300000311
a small signal component is commanded for the current of the photovoltaic converter; kpupvIs the outer ring proportionality coefficient of the voltage of the photovoltaic converter, KiupvThe voltage outer loop integral coefficient of the photovoltaic converter is obtained;
step 1.5, establishing a mathematical model of a current inner loop of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA00031301867300000312
in the formula: kpipvIs the current inner loop proportionality coefficient, K, of the photovoltaic converteriipvIs the current inner loop integral coefficient of the photovoltaic converter,
Figure BDA00031301867300000313
a closed-loop duty cycle control signal for the photovoltaic converter;
step 1.6, establishing a closed-loop impedance model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA00031301867300000314
wherein:
Zocpvclosed loop impedance for the photovoltaic converter;
Gipvfor the current loop transfer function of the photovoltaic converter, GupvFor the voltage loop transfer function of the photovoltaic converter, GudpvIs a transfer function between the duty ratio of the photovoltaic converter and the bus voltage, GidpvIs a transfer function between the duty cycle of the photovoltaic converter and the inductor current, GuipvAs a transfer function between the bus current of the photovoltaic converter and the voltage of the photovoltaic cell, GiipvAs a transfer function between the bus current and the inductor current, T, of the photovoltaic converterudpvFor a transfer function between the duty ratio of the photovoltaic converter and the voltage of the photovoltaic cell, the expressions are respectively as follows:
Figure BDA0003130186730000041
Figure BDA0003130186730000042
Figure BDA0003130186730000043
Figure BDA0003130186730000044
Figure BDA0003130186730000045
Figure BDA0003130186730000046
Figure BDA0003130186730000047
step 2, establishing an impedance model of the direct-current micro-grid energy storage converter, wherein the impedance model comprises sampling and modeling, and the specific process comprises the following steps:
step 2.1, obtaining output current i of the energy storage battery of the direct-current micro-grid energy storage converter through collectionbInductive current i of direct-current micro-grid energy storage converterLbCapacitor voltage u at input side of direct-current micro-grid energy storage converterCbCapacitor voltage u at output side of direct-current micro-grid energy storage converterdcbOutput side current i of direct current micro-grid energy storage converterdcb；
Step 2.2, establishing a main circuit mathematical model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure BDA0003130186730000048
in the formula:
Figure BDA0003130186730000049
output current i for energy storage battery of energy storage converterbSmall signal component of steady-state operating point, ILbFor the inductive current i of the energy-storing converterLbThe dc component of the steady-state operating point,
Figure BDA00031301867300000410
for the inductive current i of the energy-storing converterLbThe small signal component of the steady-state operating point,
Figure BDA0003130186730000051
for the input side capacitor voltage u of the energy storage converterbSmall signal component of steady state operating point, UdcbFor the output side capacitor voltage u of the energy storage converterdcbThe dc component of the steady-state operating point,
Figure BDA0003130186730000052
for the output side capacitor voltage u of the energy storage converterdcbThe small signal component of the steady-state operating point,
Figure BDA0003130186730000053
for outputting side current i of energy-storage converterdcbSmall signal component of steady state operating point, DbOpen loop duty cycle d for energy storage converterbThe dc component of the steady-state operating point,
Figure BDA0003130186730000054
open loop duty cycle d for energy storage converterbSmall signal components at steady state operating points;
step 2.3, establishing an open-loop impedance model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure BDA0003130186730000055
in the formula: zobOpen loop impedance for the energy storage converter;
step 2.4, establishing a mathematical model of a current inner loop of the direct-current micro-grid energy storage converter, which is specifically as follows:
Figure BDA0003130186730000056
in the formula: kpibIs the current inner loop proportionality coefficient, K, of the photovoltaic converteriibIs the current inner loop integral coefficient of the photovoltaic converter,
Figure BDA0003130186730000057
is a closed-loop duty cycle control signal for the energy storage converter,
Figure BDA0003130186730000058
a small signal component is a current instruction of the energy storage converter;
step 2.5, establishing a closed-loop impedance model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure BDA0003130186730000059
wherein:
Zocbclosed loop impedance for the energy storage converter;
Gibfor the current loop transfer function of the energy-storing converter, GiibFor transfer function between bus current and inductor current of energy-storing converter, GidbFor transfer function between duty cycle of energy-storage converter and inductor current, GudbThe expressions of the transfer function between the duty ratio of the energy storage converter and the bus voltage are respectively as follows:
Figure BDA0003130186730000061
Figure BDA0003130186730000062
Figure BDA0003130186730000063
Figure BDA0003130186730000064
step 3, establishing a direct-current microgrid direct-current simulation power grid impedance model, including sampling, coordinate transformation and modeling, and specifically comprising the following processes:
step 3.1, acquiring three-phase inductive current i at the side of a bridge arm of the direct-current micro-grid direct-current simulation power grid through the acquired direct-current micro-grid1a，i1b，i1cThree-phase inductive current i at grid side of direct-current micro-grid direct-current simulation power grid2a，i2b，i2cThree-phase filter capacitor voltage v of direct-current micro-grid direct-current simulation power gridCfa，vCfb，vCfcThree-phase alternating current power grid voltage e of direct current micro-grid direct current simulation power grida，eb，ecThree-phase output voltage v at arm side of direct-current analog electric bridge of direct-current micro-gridinva，vinvb，vinvcDC side capacitor voltage u of DC analog power grid of DC micro-gridCdcg；
For DC analog electric network bridge arm side three-phase inductive current i1a，i1b，i1cPerforming single synchronous rotation coordinate transformation to obtain a three-phase inductive current dq component i at the bridge arm side of the direct current simulation power grid1d，i1qDirect current simulation grid side three-phase inductive current i2a，i2b，i2cPerforming single synchronous rotation coordinate transformation to obtain three-phase inductive current dq component i at the side of the direct current simulation power grid2d，i2qDirect current simulation power grid three-phase filter capacitor voltage vCfa，vCfb，vCfcPerforming single-synchronous rotation coordinate transformation to obtain a three-phase filter capacitor voltage dq component v of the direct-current simulation power gridCfd，vCfqFor DC analog grid three-phase AC grid voltage ea，eb，ecPerforming single-synchronous rotation coordinate transformation to obtain a three-phase alternating current grid voltage dq component e of the direct current simulation gridd，eqFor three-phase output voltage v at arm side of DC analog electric network bridgeinva，vinvb，vinvcPerforming single synchronous rotation coordinate transformation to obtain a three-phase output voltage dq component v at the bridge arm side of the direct current simulation power gridinvd，vinvq；
Step 3.2, establishing a main circuit mathematical model of the direct-current micro-grid optical direct-current simulation power grid, wherein the expression is as follows:
Figure BDA0003130186730000071
Figure BDA0003130186730000072
Figure BDA0003130186730000073
in the formula:
Figure BDA0003130186730000074
for the three-phase output voltage dq component v of the arm side of the DC analog electric network bridgeinvdThe small signal component of the steady-state operating point,
Figure BDA0003130186730000075
for the three-phase output voltage dq component v of the arm side of the DC analog electric network bridgeinvqThe small signal component of the steady-state operating point,
Figure BDA0003130186730000076
for DC simulation of three-phase inductive current dq component i on arm side of electric network bridge1dThe small signal component of the steady-state operating point,
Figure BDA0003130186730000077
for DC simulation of three-phase inductive current dq component i on arm side of electric network bridge1qThe small signal component of the steady-state operating point,
Figure BDA0003130186730000078
for simulating three-phase filter capacitor voltage dq component v of power grid by direct currentCfdThe small signal component of the steady-state operating point,
Figure BDA0003130186730000079
is a direct current moduleVoltage dq component v of three-phase filter capacitor of pseudo-gridCfqThe small signal component of the steady-state operating point,
Figure BDA00031301867300000710
simulating three-phase inductive current dq component i at grid side of power grid for direct current2dThe small signal component of the steady-state operating point,
Figure BDA00031301867300000711
simulating three-phase inductive current dq component i at grid side of power grid for direct current2qThe small signal component of the steady-state operating point,
Figure BDA00031301867300000712
for simulating three-phase AC network voltage dq component e of network for DCdThe small signal component of the steady-state operating point,
Figure BDA00031301867300000713
for simulating three-phase AC network voltage dq component e of network for DCqSmall signal component of steady state working point, w is the angular frequency of the direct current simulation power grid;
step 3.3, establishing a d-axis voltage outer ring mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA00031301867300000714
in the formula:
Figure BDA00031301867300000715
for DC simulation of power grid DC side given voltage udcgrefThe small signal component of the steady-state operating point,
Figure BDA00031301867300000716
for simulating the DC side capacitor voltage u of the power griddcgThe small signal component of the steady-state operating point,
Figure BDA00031301867300000717
simulating a grid current command for DC，KpugFor DC simulation of the outer loop proportionality coefficient, K, of the network voltageiugSimulating the outer ring integral coefficient of the power grid voltage for direct current;
step 3.4, establishing a direct-current microgrid direct-current simulation grid d-axis current inner ring mathematical model, wherein the expression is as follows:
Figure BDA0003130186730000081
in the formula: kpigFor simulating the current inner-loop proportionality coefficient, K, of the power grid by direct currentiigFor simulating the current inner loop integral coefficient of the power grid by direct current,
Figure BDA0003130186730000082
d-axis closed-loop duty ratio control signals of the direct current simulation power grid;
step 3.5, establishing a d-axis closed loop impedance model of the direct-current simulation power grid of the direct-current micro-grid, wherein the expression is as follows:
Figure BDA0003130186730000083
wherein:
Zdcgdfor simulating the closed-loop impedance, U, of the grid by means of direct currentpccdFor simulating the d-axis component, U, of the grid-connected point voltage of the griddcgFor simulating the steady-state operating point voltage, I, on the DC side of the griddcgSimulating the steady-state operating point current, L, on the DC side of the grid for DC2dSimulating three-phase inductive current dq component i at grid side of power grid for direct current2dA direct current component of a steady state operating point;
Gigdsimulating the transfer function of the current loop of the network for DC GinvdFor simulating the grid inverter transfer function for DC, GugdThe transfer function of the voltage loop of the direct current analog power grid is represented by the following expressions:
Ginvd＝1
Figure BDA0003130186730000084
Figure BDA0003130186730000085
and 4, combining the closed-loop impedance models established in the steps 1, 2 and 3 to obtain the closed-loop impedance model of the optical storage direct current micro-grid.
Compared with the prior art, the invention has the following beneficial effects:
1. in the process of analyzing the stability of the optical storage direct current microgrid system, an impedance model is not established on the whole optical storage direct current microgrid, particularly, an impedance model is established on a direct current simulation power grid from a direct current side, and the impedance model is higher in inclusiveness compared with another state space model.
2. The modeling method for the optical storage direct-current micro-grid is simple, the impedance model is further applied to the field of stability analysis of the direct-current micro-grid system, the difficulty of the subsequent stability analysis of the optical storage direct-current micro-grid is reduced, and the method is easier to implement.
Drawings
Fig. 1 is a topology structure of an optical storage dc micro grid in an embodiment of the present invention.
Fig. 2 is a photovoltaic control block diagram in an embodiment of the present invention.
Fig. 3 is a block diagram of energy storage constant current charging and discharging control in the embodiment of the present invention.
Fig. 4 is a d-axis control block diagram of the dc analog power grid according to the embodiment of the present invention.
Fig. 5 is a bode diagram of the stability analysis of the optical storage dc microgrid of the present invention.
Detailed Description
The present invention is described in further detail below with reference to the attached drawings.
The topology structure of the optical storage direct current microgrid in the embodiment of the invention is shown in fig. 1. As shown in fig. 1, the topology structure of the optical storage dc micro-grid includes a photovoltaic converter structure, an energy storage converter structure, and a dc analog grid structure.
The photovoltaic converter structure comprises photovoltaic cells PV of the photovoltaic converter and an input side capacitor C of the photovoltaic converterpvPhotovoltaic converter inductor LpvDiode VD of photovoltaic converterpvTriode S of photovoltaic converterpvAnd a photovoltaic converter output side capacitor Cdcpy. The energy storage converter structure comprises an energy storage Battery of the energy storage converter and an input side capacitor C of the energy storage converterb1Inductor L of energy storage converterbBoost triode S of energy storage converterb1Buck triode S of energy storage converterb2And the output side capacitor C of the energy storage converterb2. The DC simulation power grid structure comprises a DC side capacitor C of the DC simulation power griddcgTwo-level three-bridge-arm inverter M of direct-current analog power grid and arm-side three-phase inductor L of direct-current analog power bridge1Three-phase filter capacitor C of direct current analog power gridfNetwork side three-phase inductor L of direct current simulation power grid2Three-phase power grid impedance L of direct current simulation power gridgAnd a three-phase AC grid e of the DC analog grid. Photovoltaic converter output side capacitor CdcpvCapacitor C at output side of energy storage converterb2DC side capacitor C of DC analog power griddcgThe three are connected in parallel.
As can be seen from fig. 1, in the present embodiment, the specific connections of the various parts in the photovoltaic converter structure are: the output end of the photovoltaic cell PV of the photovoltaic converter comprises a photovoltaic cell output direct current positive bus, a photovoltaic cell output direct current negative bus and an input side capacitor C of the photovoltaic converterpvOne end of the photovoltaic inverter is connected with a direct current positive bus output by the photovoltaic cell, the other end of the photovoltaic inverter is connected with a direct current negative bus output by the photovoltaic cell, the direct current positive bus output by the photovoltaic cell and the photovoltaic inverter inductor LpvSerially connected diode VD with photovoltaic converterpvSeries photovoltaic converter triode SpvOne end of is connected with the photovoltaic converter inductor LpvWith photovoltaic converter diode VDpvThe other end is connected with a photovoltaic cell output direct current negative bus and a photovoltaic converter output side capacitor CdcpvOne end of the first diode is connected with a diode VD of the photovoltaic converterpvThen, the other end is connected with lightThe voltage battery outputs a direct current negative bus.
As can be seen from fig. 1, in this embodiment, the specific connections of the various parts of the energy storage converter structure are as follows: the output end of the energy storage Battery Battery of the energy storage converter comprises an energy storage Battery output direct current positive bus and an energy storage Battery output direct current negative bus, and an input side capacitor C of the energy storage converterb1One end of the energy storage battery is connected with the direct current positive bus output by the energy storage battery, the other end of the energy storage battery is connected with the direct current negative bus output by the energy storage battery, the direct current positive bus output by the energy storage battery is connected with the inductance L of the energy storage converterbBuck triode S connected with energy storage converter after series connectionb2Boost triode S of series-connection energy storage converterb1One end of the inductor is connected with the inductance L of the energy storage converterbAnd energy storage converter buck triode Sb2The other end is connected with an output direct current negative bus of the energy storage battery, and an output side capacitor C of the energy storage converterb2One end of the energy storage converter is connected with the buck triode, and the other end of the energy storage converter is connected with the output direct current negative bus of the energy storage battery.
As can be seen from fig. 1, in this embodiment, the specific connections of the various parts of the dc analog power grid structure are as follows: three-phase AC power grid e of DC simulation power grid and three-phase power grid impedance L of DC simulation power gridgThree-phase network impedance L of series and direct current analog networkgThree-phase inductor L on grid side of direct current simulation power grid2Three-phase inductance L on grid side of series and direct current analog power grid2Three-phase inductor L on bridge arm side of direct current simulation power grid1Three-phase filter capacitor C of series-connection and direct-current analog power gridfThree-phase inductor L connected to bridge arm side of direct current simulation power grid in star connection mode1Three-phase inductor L on grid side of direct current simulation power grid2Three-phase inductance L at arm side of direct-current analog electric bridge1The other end of the three-bridge inverter M is connected with one end of a DC analog power grid two-level three-bridge arm inverter M, and the other end of the three-bridge inverter M is connected with a DC side capacitor C of the DC analog power griddcgAnd (4) connecting in parallel.
The electrical parameters relevant to the implementation of the invention are set as follows:
photovoltaic converter inductor Lpv0.6mH, input side capacitance C of the photovoltaic converterpv10uF, photovoltaic converter output side capacitanceCdcpv200 uF. Inductance L of energy storage converterb5mH, input side capacitor C of energy storage converterb1200uF, the output side capacitor C of the energy storage converterb2200 uF. Arm side three-phase inductance L of direct current analog electric network bridge10.6mH, three-phase filter capacitor C of direct current analog power gridf6.7uF, three-phase inductance L on the side of the direct current simulation power grid20.001mH, DC analog network three-phase network impedance Lg＝0.66mH。
Fig. 2 is a photovoltaic control block diagram in the embodiment of the present invention, fig. 3 is an energy storage constant current charging and discharging control block diagram in the embodiment of the present invention, and fig. 4 is a direct current analog grid d-axis control block diagram in the embodiment of the present invention. As can be seen from fig. 2 to 4, the modeling method for the optical storage direct current microgrid provided by the invention comprises the steps of establishing a direct current microgrid photovoltaic converter impedance model, establishing a direct current microgrid energy storage converter impedance model and establishing a direct current microgrid direct current simulation power grid impedance model, and the specific steps are as follows:
step 1, establishing an impedance model of the direct-current micro-grid photovoltaic converter, wherein the impedance model comprises sampling and modeling, and the specific process comprises the following steps:
step 1.1, acquiring output current i of photovoltaic cell of photovoltaic converter through collectionpvAnd the inductive current i of the photovoltaic converterLpvAnd the capacitance voltage u at the input side of the photovoltaic converterCpvThe output side capacitor voltage u of the photovoltaic converterdcpvCurrent i at output side of photovoltaic converterdcpv；
Step 1.2, establishing a main circuit mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA0003130186730000111
in the formula:
Figure BDA0003130186730000112
output current i for photovoltaic cell of photovoltaic converterpvSmall signal component of steady-state operating point, ILpvFor the inductive current i of the photovoltaic converterLpvThe dc component of the steady-state operating point,
Figure BDA0003130186730000113
for the inductive current i of the photovoltaic converterLpvThe small signal component of the steady-state operating point,
Figure BDA0003130186730000114
for the input side capacitance voltage u of the photovoltaic converterCpvSmall signal component of steady state operating point, UdcpvFor the output side capacitor voltage u of the photovoltaic converterdcpvThe dc component of the steady-state operating point,
Figure BDA0003130186730000115
for the output side capacitor voltage u of the photovoltaic converterdcpvThe small signal component of the steady-state operating point,
Figure BDA0003130186730000116
for the output side current i of the photovoltaic converterdcpvSmall signal component of steady state operating point, DpvOpen loop duty cycle d for photovoltaic converterspvThe dc component of the steady-state operating point,
Figure BDA0003130186730000117
open loop duty cycle d for photovoltaic converterspvSmall signal component of steady state working point, s is Laplace operator;
step 1.3, establishing an open-loop impedance model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA0003130186730000118
in the formula: zopvOpen loop impedance for the photovoltaic converter;
step 1.4, establishing a voltage outer loop mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA0003130186730000119
in the formula:
Figure BDA00031301867300001110
controlling a voltage command u for a photovoltaic converter MPPTpvrefThe small signal component of the steady-state operating point,
Figure BDA00031301867300001111
a small signal component is commanded for the current of the photovoltaic converter; kpupvIs the outer ring proportionality coefficient of the voltage of the photovoltaic converter, KiupvThe voltage outer loop integral coefficient of the photovoltaic converter is obtained;
step 1.5, establishing a mathematical model of a current inner loop of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA00031301867300001112
in the formula: kpipvIs the current inner loop proportionality coefficient, K, of the photovoltaic converteriipvIs the current inner loop integral coefficient of the photovoltaic converter,
Figure BDA0003130186730000121
a closed-loop duty cycle control signal for the photovoltaic converter;
step 1.6, establishing a closed-loop impedance model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA0003130186730000122
wherein:
Zocpvclosed loop impedance for the photovoltaic converter;
Gipvfor the current loop transfer function of the photovoltaic converter, GupvFor the voltage loop transfer function of the photovoltaic converter, GudpvIs a transfer function between the duty ratio of the photovoltaic converter and the bus voltage, GidpvIs a transfer function between the duty cycle of the photovoltaic converter and the inductor current, GuipvAs a transfer function between the bus current of the photovoltaic converter and the voltage of the photovoltaic cell, GiipvFor photovoltaic transformersTransfer function between converter bus current and inductor current, TudpvFor a transfer function between the duty ratio of the photovoltaic converter and the voltage of the photovoltaic cell, the expressions are respectively as follows:
Figure BDA0003130186730000123
Figure BDA0003130186730000124
Figure BDA0003130186730000125
Figure BDA0003130186730000126
Figure BDA0003130186730000127
Figure BDA0003130186730000128
Figure BDA0003130186730000129
in this embodiment, Kpupv＝0.5，Kiupv＝100，Kpipv＝0.1，Kiipv＝3000，Dpv＝0.318，Udcpv＝1100V，ILpv＝40A。
Step 2, establishing an impedance model of the direct-current micro-grid energy storage converter, wherein the impedance model comprises sampling and modeling, and the specific process comprises the following steps:
step 2.1, obtaining output current i of the energy storage battery of the direct-current micro-grid energy storage converter through collectionbInductive current i of direct-current micro-grid energy storage converterLbCapacitor voltage u at input side of direct-current micro-grid energy storage converterCbCapacitor voltage u at output side of direct-current micro-grid energy storage converterdcbOutput side current i of direct current micro-grid energy storage converterdcb；
Step 2.2, establishing a main circuit mathematical model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure BDA0003130186730000131
in the formula:
Figure BDA0003130186730000132
output current i for energy storage battery of energy storage converterbSmall signal component of steady-state operating point, ILbFor the inductive current i of the energy-storing converterLbThe dc component of the steady-state operating point,
Figure BDA0003130186730000133
for the inductive current i of the energy-storing converterLbThe small signal component of the steady-state operating point,
Figure BDA0003130186730000134
for the input side capacitor voltage u of the energy storage converterbSmall signal component of steady state operating point, UdcbFor the output side capacitor voltage u of the energy storage converterdcbThe dc component of the steady-state operating point,
Figure BDA0003130186730000135
for the output side capacitor voltage u of the energy storage converterdcbThe small signal component of the steady-state operating point,
Figure BDA0003130186730000136
for outputting side current i of energy-storage converterdcbSmall signal component of steady state operating point, DbOpen loop duty cycle d for energy storage converterbThe dc component of the steady-state operating point,
Figure BDA0003130186730000137
open loop duty cycle d for energy storage converterbSmall signal components at steady state operating points;
step 2.3, establishing an open-loop impedance model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure BDA0003130186730000138
in the formula: zobOpen loop impedance for the energy storage converter;
step 2.4, establishing a mathematical model of a current inner loop of the direct-current micro-grid energy storage converter, which is specifically as follows:
Figure BDA0003130186730000139
in the formula: kpibIs the current inner loop proportionality coefficient, K, of the photovoltaic converteriibIs the current inner loop integral coefficient of the photovoltaic converter,
Figure BDA00031301867300001310
is a closed-loop duty cycle control signal for the energy storage converter,
Figure BDA00031301867300001311
a small signal component is a current instruction of the energy storage converter;
step 2.5, establishing a closed-loop impedance model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure BDA00031301867300001312
wherein:
Zocbclosed loop impedance for the energy storage converter;
Gibfor the current loop transfer function of the energy-storing converter, GiibFor transfer function between bus current and inductor current of energy-storing converter, GidbFor transfer function between duty cycle of energy-storage converter and inductor current, GudbFor changing over to stored energyThe expressions of the transfer function between the duty ratio of the device and the bus voltage are respectively as follows:
Figure BDA0003130186730000141
Figure BDA0003130186730000142
Figure BDA0003130186730000143
Figure BDA0003130186730000144
in this embodiment, Kpib＝1，Kiib＝200，Db＝0.636，Udcb＝1100V，ILb＝-14.3A。
Step 3, establishing a direct-current microgrid direct-current simulation power grid impedance model, including sampling, coordinate transformation and modeling, and specifically comprising the following processes:
step 3.1, acquiring three-phase inductive current i at the side of a bridge arm of the direct-current micro-grid direct-current simulation power grid through the acquired direct-current micro-grid1a，i1b，i1cThree-phase inductive current i at grid side of direct-current micro-grid direct-current simulation power grid2a，i2b，i2cThree-phase filter capacitor voltage v of direct-current micro-grid direct-current simulation power gridCfa，vCfb，vCfcThree-phase alternating current power grid voltage e of direct current micro-grid direct current simulation power grida，eb，ecThree-phase output voltage v at arm side of direct-current analog electric bridge of direct-current micro-gridinva，vinvb，vinvcDC side capacitor voltage u of DC analog power grid of DC micro-gridCdcg；
For DC analog electric network bridge arm side three-phase inductive current i1a，i1b，i1cPerforming single synchronous rotation coordinate transformation to obtain three phases at the bridge arm side of the direct current simulation power gridComponent i of inductor current dq1d，i1qDirect current simulation grid side three-phase inductive current i2a，i2b，i2cPerforming single synchronous rotation coordinate transformation to obtain three-phase inductive current dq component i at the side of the direct current simulation power grid2d，i2qDirect current simulation power grid three-phase filter capacitor voltage vCfa，vCfb，vCfcPerforming single-synchronous rotation coordinate transformation to obtain a three-phase filter capacitor voltage dq component v of the direct-current simulation power gridCfd，vCfqFor DC analog grid three-phase AC grid voltage ea，eb，ecPerforming single-synchronous rotation coordinate transformation to obtain a three-phase alternating current grid voltage dq component e of the direct current simulation gridd，eqFor three-phase output voltage v at arm side of DC analog electric network bridgeinva，vinvb，vinvcPerforming single synchronous rotation coordinate transformation to obtain a three-phase output voltage dq component v at the bridge arm side of the direct current simulation power gridinvd，vinvq；
Step 3.2, establishing a main circuit mathematical model of the direct-current micro-grid optical direct-current simulation power grid, wherein the expression is as follows:
Figure BDA0003130186730000151
Figure BDA0003130186730000152
Figure BDA0003130186730000153
in the formula:
Figure BDA0003130186730000154
for the three-phase output voltage dq component v of the arm side of the DC analog electric network bridgeinvdThe small signal component of the steady-state operating point,
Figure BDA0003130186730000155
for the three-phase output voltage dq component v of the arm side of the DC analog electric network bridgeinvqThe small signal component of the steady-state operating point,
Figure BDA0003130186730000156
for DC simulation of three-phase inductive current dq component i on arm side of electric network bridge1dThe small signal component of the steady-state operating point,
Figure BDA0003130186730000157
for DC simulation of three-phase inductive current dq component i on arm side of electric network bridge1qThe small signal component of the steady-state operating point,
Figure BDA0003130186730000158
for simulating three-phase filter capacitor voltage dq component v of power grid by direct currentCfdThe small signal component of the steady-state operating point,
Figure BDA0003130186730000159
for simulating three-phase filter capacitor voltage dq component v of power grid by direct currentCfqThe small signal component of the steady-state operating point,
Figure BDA00031301867300001510
simulating three-phase inductive current dq component i at grid side of power grid for direct current2dThe small signal component of the steady-state operating point,
Figure BDA00031301867300001511
simulating three-phase inductive current dq component i at grid side of power grid for direct current2qThe small signal component of the steady-state operating point,
Figure BDA00031301867300001512
for simulating three-phase AC network voltage dq component e of network for DCdThe small signal component of the steady-state operating point,
Figure BDA00031301867300001513
for simulating three-phase AC network voltage dq component e of network for DCqSmall signal component of steady state working point, w is the angular frequency of the direct current simulation power grid;
step 3.3, establishing a d-axis voltage outer ring mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure BDA00031301867300001514
in the formula:
Figure BDA00031301867300001515
for DC simulation of power grid DC side given voltage udcgrefThe small signal component of the steady-state operating point,
Figure BDA00031301867300001516
for simulating the DC side capacitor voltage u of the power griddcgThe small signal component of the steady-state operating point,
Figure BDA00031301867300001517
for simulating the grid current command for DC, KpugFor DC simulation of the outer loop proportionality coefficient, K, of the network voltageiugSimulating the outer ring integral coefficient of the power grid voltage for direct current;
step 3.4, establishing a direct-current microgrid direct-current simulation grid d-axis current inner ring mathematical model, wherein the expression is as follows:
Figure BDA0003130186730000161
in the formula: kpigFor simulating the current inner-loop proportionality coefficient, K, of the power grid by direct currentiigFor simulating the current inner loop integral coefficient of the power grid by direct current,
Figure BDA0003130186730000162
d-axis closed-loop duty ratio control signals of the direct current simulation power grid;
step 3.5, establishing a d-axis closed loop impedance model of the direct-current simulation power grid of the direct-current micro-grid, wherein the expression is as follows:
Figure BDA0003130186730000163
wherein:
Zdcgdfor simulating the closed-loop impedance, U, of the grid by means of direct currentpccdFor simulating the d-axis component, U, of the grid-connected point voltage of the griddcgFor simulating the steady-state operating point voltage, I, on the DC side of the griddcgFor simulating the steady-state operating point current, I, on the DC side of the grid2dSimulating three-phase inductive current dq component i at grid side of power grid for direct current2dA direct current component of a steady state operating point;
Gigdsimulating the transfer function of the current loop of the network for DC GinvdFor simulating the grid inverter transfer function for DC, GugdThe transfer function of the voltage loop of the direct current analog power grid is represented by the following expressions:
Ginvd＝1
Figure BDA0003130186730000164
Figure BDA0003130186730000165
in this embodiment, Kpug＝1，Kiug＝10，Kpig＝0.1，Kiig＝10，Upccd＝312.6V，Udcg＝1100V，Idcg＝18.18A。
And 4, combining the closed-loop impedance models established in the steps 1, 2 and 3 to obtain the closed-loop impedance model of the optical storage direct current micro-grid.
In this embodiment, the photovoltaic converter portion in the optical storage dc microgrid operates at the maximum power and feeds power to the energy storage converter and the dc analog power grid, the stability analysis of the optical storage dc microgrid in this mode is shown in fig. 5, the upper and lower graphs are respectively an amplitude-frequency characteristic curve and a phase-frequency characteristic curve, the ordinate of the amplitude-frequency characteristic curve is an amplitude value in dB, the ordinate of the phase-frequency characteristic curve is a phase in deg, the abscissa of both the phase-frequency characteristic curves is an angular frequency, and the angular frequency is rad/s, so that the following conclusion can be obtained: in the middle frequency area, there is a certain stability margin, and in the high frequency area, the system stability margin is insufficient.

Claims (1)

1. The modeling method of the optical storage direct-current microgrid is characterized in that a topological structure of the optical storage direct-current microgrid comprises a photovoltaic converter structure, an energy storage converter structure and a direct-current simulation power grid structure; the photovoltaic converter structure comprises photovoltaic cells PV of the photovoltaic converter and an input side capacitor C of the photovoltaic converterpvPhotovoltaic converter inductor LpvDiode VD of photovoltaic converterpvTriode S of photovoltaic converterpvAnd a photovoltaic converter output side capacitor Cdcpv(ii) a The energy storage converter structure comprises an energy storage Battery of the energy storage converter and an input side capacitor C of the energy storage converterb1Inductor L of energy storage converterbBoost triode S of energy storage converterb1Buck triode S of energy storage converterb2And the output side capacitor C of the energy storage converterb2(ii) a The DC simulation power grid structure comprises a DC side capacitor C of the DC simulation power griddcgTwo-level three-bridge-arm inverter M of direct-current analog power grid and arm-side three-phase inductor L of direct-current analog power bridge1Three-phase filter capacitor C of direct current analog power gridfNetwork side three-phase inductor L of direct current simulation power grid2Three-phase power grid impedance L of direct current simulation power gridgAnd a three-phase alternating current power grid e of the direct current simulation power grid; photovoltaic converter output side capacitor CdcpvCapacitor C at output side of energy storage converterb2DC side capacitor C of DC analog power griddcgThe three are connected in parallel;
the optical storage direct-current microgrid modeling method comprises the steps of establishing a direct-current microgrid photovoltaic converter impedance model, establishing a direct-current microgrid energy storage converter impedance model and establishing a direct-current microgrid direct-current simulation power grid impedance model, and specifically comprises the following steps:
step 1, establishing an impedance model of the direct-current micro-grid photovoltaic converter, wherein the impedance model comprises sampling and modeling, and the specific process comprises the following steps:
step 1.1, acquiring output current i of photovoltaic cell of photovoltaic converter through collectionpvAnd the inductive current i of the photovoltaic converterLpvAnd the capacitance voltage u at the input side of the photovoltaic converterCpvThe output side capacitor voltage u of the photovoltaic converterdcpvCurrent i at output side of photovoltaic converterdcpv；
Step 1.2, establishing a main circuit mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure FDA0003130186720000011
in the formula:
Figure FDA0003130186720000012
output current i for photovoltaic cell of photovoltaic converterpvSmall signal component of steady-state operating point, ILpvFor the inductive current i of the photovoltaic converterLpvThe dc component of the steady-state operating point,
Figure FDA0003130186720000013
for the inductive current i of the photovoltaic converterLpvThe small signal component of the steady-state operating point,
Figure FDA0003130186720000014
for the input side capacitance voltage u of the photovoltaic converterCpvSmall signal component of steady state operating point, UdcpvFor the output side capacitor voltage u of the photovoltaic converterdcpvThe dc component of the steady-state operating point,
Figure FDA0003130186720000015
for the output side capacitor voltage u of the photovoltaic converterdcpvThe small signal component of the steady-state operating point,
Figure FDA0003130186720000016
for the output side current i of the photovoltaic converterdcpvSmall signal component of steady state operating point, DpvOpen loop duty cycle d for photovoltaic converterspvThe dc component of the steady-state operating point,
Figure FDA0003130186720000021
open loop duty cycle d for photovoltaic converterspvSmall signal component of steady state working point, s is Laplace operator;
step 1.3, establishing an open-loop impedance model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure FDA0003130186720000022
in the formula: zopvOpen loop impedance for the photovoltaic converter;
step 1.4, establishing a voltage outer loop mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure FDA0003130186720000023
in the formula:
Figure FDA0003130186720000024
controlling a voltage command u for a photovoltaic converter MPPTpvrefThe small signal component of the steady-state operating point,
Figure FDA0003130186720000025
a small signal component is commanded for the current of the photovoltaic converter; kpupvIs the outer ring proportionality coefficient of the voltage of the photovoltaic converter, KiupvThe voltage outer loop integral coefficient of the photovoltaic converter is obtained;
step 1.5, establishing a mathematical model of a current inner loop of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure FDA0003130186720000026
in the formula: kpipvIs the current inner loop proportionality coefficient, K, of the photovoltaic converteriipvIs the current inner loop integral coefficient of the photovoltaic converter,
Figure FDA0003130186720000027
a closed-loop duty cycle control signal for the photovoltaic converter;
step 1.6, establishing a closed-loop impedance model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure FDA0003130186720000028
wherein:
Zocpvclosed loop impedance for the photovoltaic converter;
Gipvfor the current loop transfer function of the photovoltaic converter, GupvFor the voltage loop transfer function of the photovoltaic converter, GudpvIs a transfer function between the duty ratio of the photovoltaic converter and the bus voltage, GidpvIs a transfer function between the duty cycle of the photovoltaic converter and the inductor current, GuipvAs a transfer function between the bus current of the photovoltaic converter and the voltage of the photovoltaic cell, GiipvAs a transfer function between the bus current and the inductor current, T, of the photovoltaic converterudpvFor a transfer function between the duty ratio of the photovoltaic converter and the voltage of the photovoltaic cell, the expressions are respectively as follows:
Figure FDA0003130186720000031
Figure FDA0003130186720000032
Figure FDA0003130186720000033
Figure FDA0003130186720000034
Figure FDA0003130186720000035
Figure FDA0003130186720000036
Figure FDA0003130186720000037
step 2, establishing an impedance model of the direct-current micro-grid energy storage converter, wherein the impedance model comprises sampling and modeling, and the specific process comprises the following steps:
step 2.1, obtaining output current i of the energy storage battery of the direct-current micro-grid energy storage converter through collectionbInductive current i of direct-current micro-grid energy storage converterLbCapacitor voltage u at input side of direct-current micro-grid energy storage converterCbCapacitor voltage u at output side of direct-current micro-grid energy storage converterdcbOutput side current i of direct current micro-grid energy storage converterdcb；
Step 2.2, establishing a main circuit mathematical model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure FDA0003130186720000038
in the formula:
Figure FDA0003130186720000039
output current i for energy storage battery of energy storage converterbSmall signal component of steady-state operating point, iLbFor the inductive current i of the energy-storing converterLbThe dc component of the steady-state operating point,
Figure FDA00031301867200000310
for the inductive current i of the energy-storing converterLbThe small signal component of the steady-state operating point,
Figure FDA00031301867200000311
for the input side capacitor voltage u of the energy storage converterbSmall signal component of steady state operating point, UdcbFor the output side capacitor voltage u of the energy storage converterdcbThe dc component of the steady-state operating point,
Figure FDA00031301867200000312
for the output side capacitor voltage u of the energy storage converterdcbThe small signal component of the steady-state operating point,
Figure FDA00031301867200000313
for outputting side current i of energy-storage converterdcbSmall signal component of steady state operating point, DbOpen loop duty cycle d for energy storage converterbThe dc component of the steady-state operating point,
Figure FDA00031301867200000314
open loop duty cycle d for energy storage converterbSmall signal components at steady state operating points;
step 2.3, establishing an open-loop impedance model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure FDA0003130186720000041
in the formula: zobOpen loop impedance for the energy storage converter;
step 2.4, establishing a mathematical model of a current inner loop of the direct-current micro-grid energy storage converter, which is specifically as follows:
Figure FDA0003130186720000042
in the formula: kpibIs the current inner loop proportionality coefficient, K, of the photovoltaic converteriibIs the current inner loop integral coefficient of the photovoltaic converter,
Figure FDA0003130186720000043
is a closed-loop duty cycle control signal for the energy storage converter,
Figure FDA0003130186720000044
a small signal component is a current instruction of the energy storage converter;
step 2.5, establishing a closed-loop impedance model of the direct-current micro-grid energy storage converter, wherein the expression is as follows:
Figure FDA0003130186720000045
wherein:
Zocbclosed loop impedance for the energy storage converter;
Gibfor the current loop transfer function of the energy-storing converter, GiibFor transfer function between bus current and inductor current of energy-storing converter, GidbFor transfer function between duty cycle of energy-storage converter and inductor current, GudbThe expressions of the transfer function between the duty ratio of the energy storage converter and the bus voltage are respectively as follows:
Figure FDA0003130186720000046
Figure FDA0003130186720000047
Figure FDA0003130186720000048
Figure FDA0003130186720000049
step 3, establishing a direct-current microgrid direct-current simulation power grid impedance model, including sampling, coordinate transformation and modeling, and specifically comprising the following processes:
step 3.1, acquiring three-phase inductive current i at the side of a bridge arm of the direct-current micro-grid direct-current simulation power grid through the acquired direct-current micro-grid1a，i1b，i1cThree-phase inductive current i at grid side of direct-current micro-grid direct-current simulation power grid2a，i2b，i2cThree-phase filter capacitor voltage v of direct-current micro-grid direct-current simulation power gridCfa，vCfb，vCfcThree-phase alternating current power grid voltage e of direct current micro-grid direct current simulation power grida，eb，ecThree-phase output voltage v at arm side of direct-current analog electric bridge of direct-current micro-gridinva，vinvb，vinvcDC side capacitor voltage u of DC analog power grid of DC micro-gridCdcg；
For DC analog electric network bridge arm side three-phase inductive current i1a，i1b，i1cPerforming single synchronous rotation coordinate transformation to obtain a three-phase inductive current dq component i at the bridge arm side of the direct current simulation power grid1d，i1qDirect current simulation grid side three-phase inductive current i2a，i2b，i2cPerforming single synchronous rotation coordinate transformation to obtain three-phase inductive current dq component i at the side of the direct current simulation power grid2d，i2qDirect current simulation power grid three-phase filter capacitor voltage vCfa，vCfb，vCfcPerforming single-synchronous rotation coordinate transformation to obtain a three-phase filter capacitor voltage dq component v of the direct-current simulation power gridCfd，vCfqFor DC analog grid three-phase AC grid voltage ea，eb，ecPerforming single-synchronous rotation coordinate transformation to obtain a three-phase alternating current grid voltage dq component e of the direct current simulation gridd，eqFor three-phase output voltage v at arm side of DC analog electric network bridgeinva，vinvb，vinvcPerforming single synchronous rotation coordinate transformation to obtain a three-phase output voltage dq component v at the bridge arm side of the direct current simulation power gridinvd，vinvq；
Step 3.2, establishing a main circuit mathematical model of the direct-current micro-grid optical direct-current simulation power grid, wherein the expression is as follows:
Figure FDA0003130186720000051
Figure FDA0003130186720000052
Figure FDA0003130186720000053
in the formula:
Figure FDA0003130186720000054
for the three-phase output voltage dq component v of the arm side of the DC analog electric network bridgeinvdThe small signal component of the steady-state operating point,
Figure FDA0003130186720000055
for the three-phase output voltage dq component v of the arm side of the DC analog electric network bridgeinvqThe small signal component of the steady-state operating point,
Figure FDA0003130186720000056
for DC simulation of three-phase inductive current dq component i on arm side of electric network bridge1dThe small signal component of the steady-state operating point,
Figure FDA0003130186720000057
for DC simulation of three-phase inductive current dq component i on arm side of electric network bridge1qThe small signal component of the steady-state operating point,
Figure FDA0003130186720000058
for simulating three-phase filter capacitor voltage dq component v of power grid by direct currentCfdThe small signal component of the steady-state operating point,
Figure FDA0003130186720000059
is a direct current moduleVoltage dq component v of three-phase filter capacitor of pseudo-gridCfqThe small signal component of the steady-state operating point,
Figure FDA00031301867200000510
simulating three-phase inductive current dq component i at grid side of power grid for direct current2dThe small signal component of the steady-state operating point,
Figure FDA00031301867200000511
simulating three-phase inductive current dq component i at grid side of power grid for direct current2qThe small signal component of the steady-state operating point,
Figure FDA00031301867200000512
for simulating three-phase AC network voltage dq component e of network for DCdThe small signal component of the steady-state operating point,
Figure FDA00031301867200000513
for simulating three-phase AC network voltage dq component e of network for DCqSmall signal component of steady state working point, w is the angular frequency of the direct current simulation power grid;
step 3.3, establishing a d-axis voltage outer ring mathematical model of the direct-current micro-grid photovoltaic converter, wherein the expression is as follows:
Figure FDA0003130186720000061
in the formula:
Figure FDA0003130186720000062
for DC simulation of power grid DC side given voltage udcgrefThe small signal component of the steady-state operating point,
Figure FDA0003130186720000063
for simulating the DC side capacitor voltage u of the power griddcgThe small signal component of the steady-state operating point,
Figure FDA0003130186720000064
for simulating the grid current command for DC, KpugFor DC simulation of the outer loop proportionality coefficient, K, of the network voltageiugSimulating the outer ring integral coefficient of the power grid voltage for direct current;
step 3.4, establishing a direct-current microgrid direct-current simulation grid d-axis current inner ring mathematical model, wherein the expression is as follows:
Figure FDA0003130186720000065
in the formula: kpigFor simulating the current inner-loop proportionality coefficient, K, of the power grid by direct currentiigFor simulating the current inner loop integral coefficient of the power grid by direct current,
Figure FDA0003130186720000066
d-axis closed-loop duty ratio control signals of the direct current simulation power grid;
step 3.5, establishing a d-axis closed loop impedance model of the direct-current simulation power grid of the direct-current micro-grid, wherein the expression is as follows:
Figure FDA0003130186720000067
wherein:
Zdcgdfor simulating the closed-loop impedance, U, of the grid by means of direct currentpccdFor simulating the d-axis component, U, of the grid-connected point voltage of the griddcgFor simulating the steady-state operating point voltage, I, on the DC side of the griddcgFor simulating the steady-state operating point current, I, on the DC side of the grid2dSimulating three-phase inductive current dq component i at grid side of power grid for direct current2dA direct current component of a steady state operating point;
Gigdsimulating the transfer function of the current loop of the network for DC GinvdFor simulating the grid inverter transfer function for DC, GugdThe transfer function of the voltage loop of the direct current analog power grid is represented by the following expressions:
Ginvd＝1
Figure FDA0003130186720000071
Figure FDA0003130186720000072
and 4, combining the closed-loop impedance models established in the steps 1, 2 and 3 to obtain the closed-loop impedance model of the optical storage direct current micro-grid.
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